If you have as many records as you say you do then, I think you might look at the Mathematica function BinCounts[]. This will group your data into discrete bins, which you can define according to your needs. You can then plot, say, C=f(A,B), using ListPlot3D[] and the results from BinCounts. BinCounts can also be used either to fit your data to a model function or for interpolation.
If you just want graphical results another way is to use Histogram3D[] to plot you data.
