Now I've asked this question here before, but since then I've lost my account, and after an hour of trying to find the answer again somewhere on this site, I thought I'd just ask it again. So it definitely is a duplicate, but I haven't a clue at how to find where this question was asked before. I apologize in advance.

The essential problem is to make your own summation command. The idea would be instead of writing \Omega_{j=1}^n which renders the j=1 to the lower right of Omega and renders the n to the upper right of Omega, I would like to have them indexed beneath and above, respectively. Exactly how the command \sum is rendered, except I don't want a capital sigma, I want a capital omega.

I can't remember how I did it before, and I recently lost the Latex files for a document I wrote using this command incessantly. I'm now in the midst of reconstructing the Latex file from the PDF and I can't for the life of me remember how I made this command.

Any help would be greatly appreciated.