PMTS: 50% upon order 50% on delivery

I was wondering if anybody has figured out how to set up a payment of 50% upon order and 50% upon delivery. We customize our products to the clients specification (granite structures). A combination of online pmt of 50% and then direct contact payment for remaining value is probably the only viable option but how would we set up the 50% pmt?

Cheers,
Lasa

I tried to set up a default option as a minus 50% but it does not accept percentage. (or "I" couldn't get it to accept %)..
I would like to have the cart require a 50% payment.
Cheers,
Lasa

Still having issues trying to set up the first 50% upon order. I was thinking maybe I could put discount 50% but then I would probably need to put a huge disclaimer explanation or people will be confused. We are selling huge granite structures.

Some body must have had this situation.

Wondering if I need a call for ordering and remove the cart all together.
Cheers,
Lasa