Dose any body know how to tell weather a cross has taken. I read that the flower is supposed to wilt and fall off. Is their any other sure way to tell?

actually, with any crosses i've made, the flower persists but wilts....
this thread shows some cyp pollinations...
http://slipperorchidforum.com/forum/showthread.php?t=9671

The flower will wilt eventually and could fall off. Personally I wouldn't pull it off for a couple months as I don't know how long it takes for the pollen tubes to form and finish the journey to the seedpod. The stem and seed pod will not turn brown if all is well. Depending on the orchid, the seedpod will need 6-12 months to mature so if it turns brown shortly after the cross, it didn't take.