2 gateway, How to use it in "TMG"? help

I have two providers for internet:

1- ADSL
2- FiberLine

I want to make group of users be on the Fiber line, remaining on the ADSL line.

Using forefront TMG>>>>>

by use ISP Redundancy or other, I don't care, it is important to identify each user on line what I want for each users.

Possible? if yes,,, how?~~~