Restrict macro to one workbook

Hi.

I'm in a situation where i have to have multiple excel workbooks open at the same time. For arguments sake i'll call them workbooks 1, 2 & 3.

Workbook 1 has an ontime macro which displays a pop up at specific periods...a sample of the code is here:

Please Login or Register  to view this content.

Workbooks 2 & 3 are purely open for data entry whilst workbook 1 runs in the background, displaying the pop ups as and when if that makes sense.

The problem i'm having is that if i enter a value in say cell D6 on workbook 2, the macro runs when i don't need it to!

How do i restrict this macro to run purely on workbook 1 irrespective of the what other workbooks/sheets are open?

I'm very new to macros and am a bit stumped!!!!

Thanks in advance!!!

Sam

Thank you very much!!
works perfectly!!