The trick is to either check for related records just before the GTRR or an error code immediately after.
You either use:
If [ not IsEmpty ( RelatedTable::NeverEmptyField ) ]
Other code here
code you want if there are no related records here
If [ Get ( LastError ) = 0 // 0 means no error code returned ]
Rest of script if there are related records
Script for if there are no related recrods
For more on GTRR, see: The Complete Go To Related Record
This works fine, both options. I couldn't find the Get (LastError) at first because of the strange translation. But I found it and it is working.
Thanks again Phil,