Hi there,
to be honest I don't think you can do what you want and I feel it is an either or situation.
For a start, how will the system know which of the cards is meant to be used?
Also there is the very real possibility of driver conflict as both cards will try to take control and fight for system resources. I cannot see how you can assign the different cards and drivers required to specific programs to alleviate this.
I stand to be corrected, but I really don't think this can be done at present.