MB21 Reservation Should not created if stock is not available

Dear Guru,

My requirement is, not to allow create reservation is stock is not available, this is specific to movement type 221.

I have configured the message type m7 181 as error message, and also set B, in dynamic availability check in SPRO of reservation node.

But when I am creating the reservation more than stock quantity (Unrestricted stock), reservation get created, system doesn't give any warning or error message.

Is there something missing, please help in this regards.

Thanks in advance

Nari