Please help me figure out the financial model I need.

I'm in school for my MBA, but right now I am in need of a portfolio optimization tool for a hobby of mine. I'm just not sure what to look for. I think the easiest thing to do would be to describe what I need and hopefully someone can tell me what I need to look for.

My goal is to be able to find a tool that can optimize a portfolio with some specific criteria. The portfolio involves several asset classes with several assets available in each class. To create an optimal portfolio, I will need the model to include a fixed number of assets from each class, such as 1 asset from one class, two from another, etc.

There are a lot of financial models out there. Can anyone help me define what type of financial model it is that I need?

Thanks in advance. I appreciate the help.