Hi Paul,

I'm sorry to hear that you're having trouble with the Compare and Merge Workbooks function in Excel. There could be a few reasons why this function is greyed-out and not working for you. Here are some possible solutions:

1. Check if both workbooks are open: The Compare and Merge Workbooks function requires that both workbooks are open in Excel. If one of the workbooks is closed, the function will be greyed-out. So, make sure that both workbooks are open before trying to use the function.
   
2. Check if the workbooks have the same structu The Compare and Merge Workbooks function only works if the two workbooks have the same structure. This means that they should have the same number of sheets, and the sheets should have the same names. If the workbooks have a different structure, the function will be greyed-out.
   
3. Check if the workbooks are protected: If one or both of the workbooks are protected, the Compare and Merge Workbooks function will be disabled. So, make sure that the workbooks are not protected before trying to use the function.
   
4. Check if the add-in is installed: The Compare and Merge Workbooks function is not a built-in feature of Excel. It is an add-in that needs to be installed separately. To check if the add-in is installed, go to the File menu, click Options, and then click Add-Ins. Look for the Compare and Merge Workbooks add-in in the list of installed add-ins. If it's not there, you'll need to install it.
   
5. Try repairing or reinstalling Excel: If none of the above solutions work, there may be a problem with your Excel installation. Try repairing or reinstalling Excel to see if that fixes the issue.

I hope one of these solutions works for you.