Auto Free ticked in PO for particular Vendor

Hi Friends,

We have a lots of vendor, All vendor takes payment.

But one of them comes relationship with our MD.

So the vendor don't take payment.

We have to treat his company as a Vendor,

So I want to go with the "FREE" option in purchase order.

Then all stock accounts are hit, but it will not hit on GR/IR or any types of external activity.

I want to make this field auto ticked for this particular vendor.

How can it possible?

Thanks

DEV