@Kitonum 

But that is not what I want; what I want is for some command to take expressions like x[1]^2+x[2]^2+x[3]^2 (resulting from previous operations) and rearrange them as Sum(x[i]^2,i=1..3).

Regards

Rudnei

@Preben Alsholm Thank you, that helps a bit. It's not in the "sum" format I would like but it's better.