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Operations Research Models and Methods
Computation Section
In Case of Trouble
Unit Incorrect installation of add-ins

It is wrong to load an add-in by double clicking its icon or opening the file through the Open command under the File menu. Correct operation requires that the add-in be loaded through the add-in dialog under the Tools menu. Alternatively, the add-in can be loaded and unloaded by pressing buttons on the Add ORMM dialog.
Unit Mismatched versions of the add-in and Excel

You cannot use the add-ins with Excel 5. or 7. The add-ins were programmed for Excel 97 for Windows and Excel 98 for the Macintosh. The add-ins have been run successfully on Excel 2000, Excel 2004, Excel XP, and Excel 2007 for Windows and Excel 2007 for Vista. They also run on Excel 2001, and Excel 2003 for the Macintosh OSX. Unfortunately Excel 2008 for the Macintosh does not include VBA, so the add-ins can't work for that version. Microsoft promises that the next version for the Macintosh will have VBA. Until that time, I continue to use Excel 2003 for development. The Mac version of VBA does not include all the features of the Windows and Excel VBA versions. It appears that the Mac version runs successfully on Windows and Vista. Since I use the Mac and try to run on Vista only occasionally, I appreciate notice of any errors you may experience on the PC. The recent revisions have not been tried on versions before Excel 2003, I can't be sure that everything is backward compatible.
Unit Errors when using the Excel Solver

There are a variety of error messages that come from the Excel Solver. A common message is that the model does not have the linear form. This occurs only when the "Assume Linear" option is selected. We have discovered that this sometimes happens even when the model is linear. One cause is very large coefficients, constraint limits or variable limits. Try to reduce the magnitude of these limits to values as small as consistent with the model purpose.
Unit Errors in automatically loading and solving with the Excel Solver

Before a math programming model is loaded or solved it is necessary to establish communications with the Excel Solver by opening and closing its dialog box. This only needs to be done once each time Excel is opened. If you forget to do this, an error message will be displayed when an add-in tries to use the Excel Solver.
Unit There are errors in the data

Please read the instructions to make sure you understand what data is to be provided. If numbers are required, do not use letters.
Unit Some formulas have been overwritten by the user

Parts of the worksheet are colored yellow to identify ranges that are not be changed. If you change a formula, there is no way to anticipate the effects.
Unit Cutting, Pasting and Duplicating worksheets

Students sometimes cut and paste areas of the worksheet. This can disturb the named ranges on the worksheet and cause the programs to fail. If you think this might have happened, create a new worksheet with different names. Copy the data from the old worksheet and paste it in the new one. Use the paste special option on the edit menu and paste only values from one place to another. Do not copy yellow areas on one worksheet to another. The add-ins assign many names to ranges that are prefixed by the worksheet name. If you duplicate worksheets the resultant worksheet will not work.
Unit Bad names are provided by the user

A number of the add-ins ask for names to be used for identifying features of the model. These names must satisfy the Excel requirements for naming ranges. Please do not use spaces or punctuation. Start names with a letter. If some feature of the workbook is assigned a name do not change it. This is particularly true for math programming models that name worksheets. Once the worksheet has a name, do not change it.
Unit Buttons on a worksheet do not work

Many of the add-ins place buttons on a worksheet. When opening a worksheet on a computer different than the one on which the buttons were created, the buttons are no longer operable. Choose the Relink buttons command from the OR_MM menu for the add-in that you are using. This will create new buttons that will be operable. This problem will be observed for the Chapter and Demo worksheets provided with this CD. Always use the Relink buttons command before proceeding. Note that the add-in creating the buttons must be installed for this to work. Recent versions of the add-ins are equipped with Start and Finish commands. The Finish command deletes all the buttons in the workbook. The buttons can be recovered with the Start command. The Start command only replaces the buttons for worksheets constructed by the particular add-in from which the Start command is selected.
Unit User Defined Functions on a worksheet do not work

Some of the add-ins provide user defined Excel functions. When a worksheet obtaining these functions is opened on a different computer than the one which created the functions, the functions may not work. Select a cell with a user defined function. Retype the "=" at the beginning of the function and the function will be repaired. Note that the add-in creating the function must be installed for this to work. If this fails, you may have to recreate the worksheet. In some cases the Relink or the Start command will correct the references to user defined functions.
Unit Too many add-ins are loaded at one time

Add-ins require memory. If you begin to get memory errors or the computer crashes, it probably means that you have not allocated enough memory to Excel or you have too many add-ins installed. Either increase the memory allocation or only install the required add-ins. Close all unnecessary windows and applications before staring Excel. The later versions of the operating system do not provide tools for changing the memory allocation. I'm not sure how memory is allocated between programs, but it is always best to install only the add-ins that you are currently using.
Unit More than one version of an add-in on the hard disk

Once Excel has found an add-in, the path to the add-in is stored by Excel. When you have more than one add-in with the same name, it's hard to know which one Excel is referencing. If you are experiencing this kind of error, use the "find" utility of the computer to find all versions. Then delete all but the latest. When Excel uses an add-in, I think Excel copies the add-in to a different place in memory. Even if a new version replaces the old, Excel still seems to address the old one. If you think that is happening use the Browse or Search button provided by the Add-in Installation procedure to locate the new version of the add-in rather than attempting to install it through the control add-ins. Then Excel will ask if you want to replace the version of the add-in currently in use. Say Yes to the question.
Unit There are errors in programming the add-ins

Despite our best efforts, there may be bugs in the program. If you think you have found one, please let the authors know. Please include the following information:

Name of add-in

Date of add-in (See the About Add-in item on each menu)

Version of Excel (97, 98, 2000, 2001, 2003, 2005, 2007)

Type of computer and operating system

At what point in the process does the error occur? (Beginning, end, during solution, etc.)

Error message

Any other things that might be relevant and would help me to track down the problem.

Unit Fix the Error yourself

When there is an error, Excel will often notify you that the error has occurred through a dialog. You can often fix the error yourself. Go to the VBA editor via the Add-ins command on the Tools menu. For Excel 2007 you can get to VBA via the Developers tab. The add-ins that are installed are listed in the Explorer panel. Click on the name of the offending add-in. Enter the password ppp. All the add-ins have the same password. Then return to Excel. Choose the add-in command that caused the error. This time the dialog box makes the Debug button live. Click that button and you will be taken to the VBA line causing the error. You may be able to fix the error. If you can't fix the error disable the command by placing an apostrophe before the command. Then try again. If the add-in doesn't work as expected delete the apostrophe and let me know. If it does work, send me an e-mail so I can fix it for other people. Before leaving the VBA editor, save the corrected add-in.

Unit If all else fails, send me a message

I can only fix error that you tell me about. Use the form above to tell me as much as you can about the error. I really do appreciated it. Others who are trying to use the add-ins appreciate it too.

I am at:


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Operations Research Models and Methods
by Paul A. Jensen
Copyright 2004 - All rights reserved

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