Thanks Bill, it seems to work. I just have to extend the code you've given to suit something like:
A={{A00,A01,A02},{A10,A11,A12},{A20,A21,A22}}
and
B={{cA11-dA22 , eA01, fA02},{gA10, hA11+jA22, kA12},{lA20,mA21,nA11-oA22}}
where a,b,c,d... are simple coefficients and A00,A01... are the 9...