Software to study Synergism between drugs - (Jun/04/2006 )

Does any one has information of any free/ trial software to study synergism between two drugs such as Combitool , Calcusyn etc.
Thanks.

Hi,
I am also in need of such a software and Calcusyn looks quite comfortable, but I can not afford 300$ for such a program I will only use for 2 times.

Does anyone know how to compute those Combination indices (CI) with Excel or something like this? I have really problems to understand the mathematical theory behind Chou and Talalay's approach.

It would be nice if anyone could help me out here...