Quote Originally Posted by I_Love_My_Vans
Um, a computer can, believe it or not only do one thing at a time, so one has saved the excel spreadsheet, and the other has to be dissapointed. I think that is how it works

Can you not try and work around the problem by overwriting or checking to see if the file exists, and declining access if it does exist.

ILMV
This is just flamebait... Moving on.

To the other people who actually understand my problem and provide meaningful solutions, thank you very much. I will look into the API and sample code for mutexes. I will also check out semaphores (its been a while since I was in OS class, so I completely forgot about these).

Also I should clarify; the two VB apps are trying to save different spreadsheets that are open in one Excel process. That is, there is a single Excel process which contains all open spreadsheets.