Error Message at Sales order

Hi Experts,

I want to set a error message at sales order level if say material A having base unit of measure NR(piece).

When user will to create a sales order for say any partial quantity say 0.5, 1.5 ,2.5, etc...

The user should get error message that "Please take the round quantity for material A " & should restrict to create Sales Order.

I have tried to do by maintaing the Deliver unit =1 at sales org .1 tab of material master.

The system gives normal message but if ignored it allows to create a sales order.

But our requirement is to restrict to create a sales order with partial quantity.

Your reply is highly expected & appreciated.

Regards