Mandatory Stored Procedure

Dear Experts ,

I am trying to make U_brd in my sales order mandatory, but its not comnig . Can someone tell me the error

IF @transaction_type in ('A') AND (@OBJECT_TYPE='17')

BEGIN

If exists (SELECT T0.[DocNum] FROM ORDR T0 left join RDR1 T1 on T1.[DocEntry] = T0.[DocEntry] where T0.DocEntry = @list_of_cols_val_tab_del and T1.[U_BRD] is null)

BEGIN

Select @error = 37, @error_message = 'ERROR: Attachment is Mandatory'

END

END