speaking of testing blank fields, any ideas what i’m missing about

CASE WHEN {custentity_os_delcode} = '' THEN CONCAT(15000, {entityid}) ELSE CONCAT(150, {custentity_os_delcode} END

? which is basically just to say, if the delcode custom field is blank, append 15000 to {entityid}; if it is populated, append 150 to custom field {delcode}