Structure/component For Performing Complex Calculations?

I hope this is the right forum. I've been developing something for a while now, and I've hit some walls with the direction I was going. I'm not an expert in .Net, so I was hoping maybe there's a nice solution that I had no idea of its existance.

A little bit of background: I'm building a relatively large scale calculation component which used to be in a spreadsheet. It composes of about 1300 values, about 150 which are passed in to the component, and the remaining 1150 are calculated based on these inputs. However, these values can be in multiple rows, as in there will be multiple rows of these 1300 values. Aggregate calculations need to be performed on these rows on a regular basis. Right now I'm using a dataset to perform this since it supports multi-row calculations nicely, but it has its limitations. It doesn't support some of the mathematical functions that I need it to perform (such as exponential) and performing a calculation like a weighted average is a hassle because you need to add a new field for it. Furthermore it doesn't let you use custom variables in your expressions, so if you want to create an on/off switch for something you need to create a single row table and set up a relationship to it. Also I'm getting tired of the dataset designer being riddled with bugs, and it's obvious to me that it was not meant for calculations of this magnitude. Not being able to see the data type of the field in the designer is a minus too (you have to bring up the property window on that field). I looked in to just creating classes to perform this, but the problem is that it needs to be relatively dynamic, and the calculations need to refresh based on user inputs. The best way I can think of doing this is setting up the 1150 calculated variables as properties so that they will be calculated automatically. But, I'm afraid that this is going to fire off thousands of calculations each time any variable is accessed, which is going to be a rather significant performance hit.

So, my question is whether anyone knows of a good structure or component that I could use to achieve my goals. I apologize if I didn't do a very good job explaining my situation, so I'll try to elaborate on any of my explanations if anything is unclear.