Yes, you need something like
If ( Regexp(GetEventVariable( {U 7} ), {S \"^\([[:alpha:]].*?\)[:.]\"})),\
CreateEventWithVariables( \ .... your procedure here),\
CreateEventWithVariables(\ ... alternate procedure if there is no match ))
The RegExp function will check if the regex matches and returns true/false rather than an error. If true, you continue with what you already have but if false, you'll need to have something else. Apologies for the very liberal use of pseudocode but hopefully it makes sense.
-Rob