From the corporate KnowledgeBase article "How to use wildcards when creating exclusions in McAfee VirusScan Enterprise 8.x" (https://kc.mcafee.com/corporate/index?page=content&id=KB54812)
Exclude the Temp folder in any location, on any drive: **\Temp\**
In this example the following directories would be excluded:
c:\documents and settings\Administrator\Local Settings\temp
I believe what you want is:
This should resolve to any folder starting with 'datatest' anywhere in the folder structure on any drive. The trailing backslash is very important.