Auto Free Goods Tick in PO

Hi Masters,

i have a requirement.

For certain material/vendor combination when the PO is created , automatically "Free Goods" checkbox should be ticked.

I have read some posts on this, also maintained the config / master data settings / Condition records.

But it adds some free goods to the original line item in PO.

Eg if i create PO for Material A for 10 qty.  another line Item gets added with Qty 5 as free goods. ( I have maintained a condition record )

But i want when i create a PO for Material A / vendor A combination, all the 10 quantity should automatically be marked as free goods.

How can i achieve this ?  Is there any standard way ? Or will i have to go for any enhancement ?

Thanks