Interaction Energy

Dear Sir,

I am doing single box NPT simulation of a mixture of ethanol and butanol
using Monte Carlo simulation. I am using TraPPE force field.
I want to calculate the interaction energy between:

Ethanol-Ethanol
Butanol-Butanol
Ethanol-Butanol.

In TraPPE force field, bond length is fixed. Bond angle follows harmonic
function while dihedral follows OPLS type function.

Is there any tool which can be used for this purpose?

Thanks,
Anand