Multiple Purchase req for MTS material after MRP run

Hi,

How is it possible to get multiple purchase req for a material which has following settings

zero stock, subjected to procurement from another plant thru STO.. and requirements are fed thru end customer Sales order(no forecast, no PIR).

i.e If i get requirement for that material thru 3 SO then I want to three purchase requisitions created after MRP run.

Please give your valuable suggestions.