Thanks for that Oorang.
It looks good, but I am working with restriction where I can not put anything into new modules - it all has to be in the ThisWorkbook module. Also, I am looking to minimize the impact this will have on the user. If it were one workbook, I would consider implementing what you have suggested, but this is going to be rolled out to over a hundred workbooks internationally, so if we change anything about how Excel operates (like how to insert new worksheets), we kind of have to retrain them.
The solution I have come up with is that each time the user moves the selection, the SelectionChange event tests for the presence of the change log. If it's not there, the user is informed "You have removed the change log. This action is not permitted as it circumvents change tracking. This workbook will now close without saving.", and the workbook closes. It's not the ideal solution (ideally, Excel would have a BeforeSheetDeletion event, which I would use), but it will work OK.
Thanks anyway!
Rob