Excel add-ins (.xla and .xlam) must first be converted to workbooks (.xls and .xlsm) before using DiffEngineX to compare them. The steps to achieve this are described below.

1. Use File->Open to open the file in Excel.
2. Click the Developer tab and then the Visual Basic button. (Excel 2003: Tools->Macro->Visual Basic Editor.)
3. In the Project Explorer window in the Visual Basic Editor, you will see an entry similar to VBAProjectName(Add-in file name *.xla). Click the plus sign to the left of this. You may need to enter a password at this point.
4. Expand Microsoft Excel Objects and click ThisWorkbook.
5. From the Tools menu select VBAProjectProperties... .
6. Select the Protection tab. Uncheck "Lock project for viewing". Clear both the password and confirm password boxes.
7. In the Properties window change the value of IsAddin from True to False. (Make sure ThisWorkbook is selected in the Project Explorer.)
8. Select "Close and Return to Microsoft Excel" from the File menu.
9. For Excel 2007 and later select File->Save As and then select Excel Macro-Enabled Workbook (*.xlsm). For Excel 2003, select File->Save As and then Microsoft Office Excel Workbook (*.xls).

Once your Excel add-ins (*.xla and *.xlam) are converted to Excel workbooks (*.xlsm or for Excel 2003 *.xls), you can use DiffEngineX to compare them. Click here for instructions on how to do this.