Hola, María.
Intenta con este bloqueo:
if @object_type in ('46') and @transaction_type in ('A','U')
Begin set @Aux1 = 0 --- No permite generar pago si el check de Bloquear pago esta activado set @Aux1 = (Select count(T1.DocEntry)
From OVPM T0
INNER JOIN OPCH T1 ON T0.[DocEntry] = T1.[receiptnum]
where T0.DocEntry = @list_of_cols_val_tab_del and t1.PAYBLOCK = 'Y' )
if @Aux1 > 0
Begin set @error = 104
select @error_message = 'Pago de Factura Bloqueado'
End
end