Free Goods Requirement

Dear Friends

The following is the requirement:

Let's assume, a business gives 2 goods free, for every 10 goods, ie 10+2 (Exclusive)

In the Std System, when we do delivery for those 10 goods, the system allows to process the delivery, though the 2 free goods are NOT available.

The requirement is,

if those 2 free goods are not available, then the system should NOT process the outboud delivery.

Requesting guidance & help, on this.

Rgds

Sumanth.G