Hi Andrew,
You can give you field as parameter to TESTFIELD function where you want to control empty value.
If it is empty it will automatically trigger an error.
TESTFIELD(stock);
-----------------------------------------
Best Regards,
Salah Eddine BENOUALA
Dynamics NAV & 365 Business Central Consultant
Please verify my answer, if you find it helpful.
Doing so you'll show others that there was found a solution and you credit my help.