PR to PO

Hi Friends,

I have created a PO with reference to PR.I once again created PO with the Same PR. It is allowing, so I have Made

00 06 076 Materials of requisition & item & alr. ordered in full

00 06 400 Materials/services for requisition & & already ordered with & &

and set "E" as category .

Now system is not allowing to create PO with reference to same PR again.

But If I create PO for partial quantity, it is not allowing for the remaining quantity.Suppose PR quantity is 5. I have created PO for 3. If again I want tocreate for remaining 2, it is not allowing. Please suggest...

Regards,