How do i set up matrix in c from equations i give it?

i want to get temp distribtion of a block so i need to set up a series of nodes and use equation T(m,n+1)+T(m+1,n)+T(m-1,n)+T(m,n-1)-4T(m... and other times equal to some value.i have program to solve using gauss elimination but i dont know how to get into form Ax=B .

How do i set up matrix in c from equations i give it?
a x b formula javascripted?

sweet pea