Restriction of number of POs for a single Sales Order

Hi,

Currently, For a Single Sales Order multiple Purchase Orders are being created. Now, the Client wants to restrict number of Purchase Orders for a Single Sales Order that means, he wants only 1 Purchase Order for 1 Sales Order. Could you guys suggest how can I do this..? Is there any configuration for this ? Please suggest.

A quick reply would be very helpful.

Thanks in advance.