Looking for PC's that DO NOT have ____.Exe

Hello,

I setup a file search for Outlook.exe using three different paths (one for each edition that could be present).  Then I set up the dynamic search group using the filters:

File > Name > Does Not Contain > Outlook.exe

This returned 140 results, 35 of which do in fact contain Outlook.exe.

I then flipped the filter to:

File > Name > Contains > Outlook.exe

This returned 35 results.  This is accurate as far as I can tell (spot checked the HDD's manually).

My problem here is that I need to push a 3rd party software to PC's that DO NOT have Outlook.exe.  I can't use Office xxxx as the filter because in our setup users get Office xxxx custom installed to exclude Outlook.

What am I doing wrong? 

Thank you,

-Ed