Not all validation checks work when in find mode and this is one of the ones that don't.
You could make your field a pop-up menu and that will preclude the possibility of entering a non-existent value.
Unfortunately the Equipment_table has too many rows for a pop-up. I think I'll try a separate find on the Equipment_table for the validation, then switch to the Equipment_Issues_table. Thanks for the info!!
You could also make it a global field and then your script need not be paused in find mode for the user to enter criteria.
Your script could use any number of such global fields to set up your find for the user:
Enter Find Mode
# Equipment_Issues::gEquipmentID must be a global field in order for this to work.
Set Field [Equipment_Issues::EquipmentID ; Equipment_Issues::gEquipmentID ]
Set error Capture [on]
Thanks! I'll try it.