I want to use the Workbook.Activate application event to detect when a
worksheet has been activated, and then depending on which one, do something...

I have seen reference on this site to catching this event in the
"ThisWorkBook code module", but I don't know where that is. I tried creating
a module with that name, and told me that it was already in use.

I'm sure that I am missing something that should be obvious, but where is or
how do I create the "ThisWorkBook" code module.

Thanks,
Steve