*Important* Transmission Leak

[mr_man]

I was driving down the street today on the way to a friends house when my transmision started poring out fluid and smoking(this was just the fluid getting on my exhaust pipes) thankfully this was almost to his house, but in about 7 blocks i lost probably almost all of my transmission fluid. We took off the transmission pan and replaced the gasket, because it wasn't obvious where the leek was, but it still leaked after that. It only leaks while driving, not in nuetral, park, or drive if my vehicles not moving. We seemed to have narrowed it down to being a line, because it's coming from the front part of the transmission, but not from the front seal. Anyone have a clue if we have a line that's known for blowing or anything? I'm having my friend tow it a transmission place tommorrow (I have classes i need to be at tommorrow). Assuming that all it is is a line, about how much money am I looking at for a fix? If anyone has any suggestions, it would be greatly appreciated. Thanks