And by chance, cannot be your problem described (simplifying) as:
you measure two parameters, say x and y, and from them you need to determine three more values q, r, s. The relations are very complex, but you do the calculations easily in matlab. The result is a set of three matrices q(x,y), r(x,y), s(x,y).
If it is so, then you don't need to perform the complicated calculation on the microcontroller itself (hence you need no matlab-C-51 conversion). Rather, you simply look up a value in the tables for q, r and s for each measured x and y - this is simple and a 51 can cope with it easily.

Of course you have to store the matrices somewhere - this is where the EPROMs come...

Can this be your case?

Jan Waclawek