I thought of using grepmatches[1-6] but I am uncertain how to us it in the middle of a file name eg
"...Unapply\NBS Building 5.5. & grepmatches[1-6] & .PWR")

Exists <Registry Value> "HKEY_LOCAL_MACHINE\SOFTWARE\Lanovation\PictureTaker\Users\%username%\Unapply Files\\68E037F1-09E4-4133-B30E-2C00169F9602". If the value exists, it means a package containing user-specific data has been installed, and there is a separate rollback file for that user's data.

The number in red needs to be changed to the unique identifier for your package. To find out the number, simply open the NBS Building 5.5.PWC file in the Editor, go to File|Properties|Information, and look at the unique ID value. 

Let us know if this helps you out.

Thank you for providing more information about what you’re trying to accomplish. As mentioned in the earlier reply, there isn’t a way to combine the use of "exists" and "grepmatches."

Perhaps the easiest way to find out if systems need to be updated is to check the version of the application’s main executable. For example, if laceName w:st="on">NBSlaceName> laceType w:st="on">Building'laceType>s main executable is nbsbuilding.exe, you could make a configuration group based on a rule like this:

(EXISTS <File> "C:\Program Files\NBSBuildingbsbuilding.exe")

AND 

(<File Version> "C:\Program Files\NBSBuildingbsbuilding.exe" < "5.1.3")

Otherwise, you could create a compound rule to look for the existence of previous versions' rollback files, and the non-existence of the most version's recent rollback file. Here’s an example:

((EXISTS <File> "%allusersprofile%\Application Data\Prism Deploy\Unapply\NBS Building 5.5.1.pwr") OR  (EXISTS <File> "%allusersprofile%\Application Data\Prism Deploy\NBS Building 5.1.2.pwr")) AND  (NOT EXISTS <File> "%allusersprofiles%\Application Data\Prism Deploy\Unapply\NBS Building 5.1.3.pwr")

Let us know if this helps.