I need G2 to start counting DOWN when F2 is 150 days out from TODAY's date
F G H
1 Exp. Date Req Due to Terminal Request Rec'd
2 10/31/08 -99 07/21/08

and then stop counting when H2 gets populated with a date (in theory, the
requests will come in way before F2's dates, such as in the above instance)

of course, with making sure G2 stays blank if:
1. F2 is blank AND
2. F2 is more than 150 days from TODAY

Is this even possible?!