I have built an application that produces separate workbooks of financial
data for each of our contracts on a monthly basis, approximately 300
workbooks per month. This application runs fine and very fast. However, I
need to make a couple of changes to it. When I save the file under a new
name (even just saving an unaltered copy) as a backup, the saved copy runs
very slowly.

I've stepped through the code and it appears to be slowing down on the
Application.CalculateFull command. However the calculations and formulae are
in a different workbook and should not be affected by me changing the
application filename.

Can anyone explain why this is happening and/or suggest a solution please?
This is a very urgent piece of work.

Thanks