@ecterrab Thanks for that. I will try that now.

A bit off-topic now I think - I have looked at the Physics tensor package, and it mostly does what I need (I am not a physicst so most of the examples are gibberish to me).  However it's main limitation for me is that you can only define one range for summation for all indices, not individually.

e.g. I want to apply the summation notation to A[i,j]*B[j,k]*C[k,m] with j=1...3 but only k=1..2