No worries, I managed to cobble together a couple of DLLs via Pascal that do the job.
As a test to see if ExtremeGammon really was pulling dice from my DLL or making it up as it went along, my first DLL didn't generate random numbers, I hardcoded a 4 and a 2 for every dice roll.
Sure enough, playing the game actually stalemated in the end because neither of us could move....but every roll was 4-2.
My second test was to eliminate doubles. A simple bit of code that said "if dice 1 = dice 2 then roll again". Again, I played several matches using this DLL without a single double being rolled.
So despite my initial scepticism of this progrma, I have to reluctantly admit that I am not as good a player as I thought I was, I've been getting my ass kicked by ExtremeGammon and it hasn't been cheating.