I was wondering if there are any tips out there to allow faster
execution of VBA with several workbooks open?

For example, I have a macro that deletes some cells contents in five
different sheets in the same workbook.

With no other workbooks open it takes 2 seconds to complete.
With other workbooks then it takes more than 10 seconds to complete.
This is just an example.
Obviously the fact that there are other workbooks open has an impact
on the execution.
Any way to speed up this?