Formula error on a WF - trying to add '-001', '-002' etc each time an order is amended and saved however getting invalid expression for formula: CASE WHEN REGEXP_LIKE({custbody_123}, '^[0-9]+$') THEN {custbody_123} || '-' || LPAD((TONUMBER(RIGHT({custbody_123},3)))+1, 3, '0') ELSE {custbody_123} END To start with custbody_123 would have something like '123456789' as a value... any ideas?

Suggest you strip this down part by part, check to see if just

LPAD((TONUMBER(RIGHT({custbody_testnum123},3)))+1, 3, '0')

works by itself etc