Adding Right Feature Condition

HI ..... 

Using WISE 6.2, I have created a property "CHECKEXE" in system search to look for "ABC.exe" file, if it finds ABC.exe does not install the feature2. I added condition for the feature2 by going to the Feature> Add Contidion entered: NOT CHECKEXE.
To make sure my system search works alright, I added property [checkexe] on welcome dialog. I get the right path if ABC.exe exists but still the feature get installed. I think the condition: NOT checkexe is not set alright. could someone help to set the condition.

I also need to make sure the feature is not uninstalled if is not installed by this MSI.

Thanks.