I am trying to solve the following equation in VUMAT

dT/dt = P*Laplacian(T) + Q* dR/dt

where Laplacian(T)=d^2(T)/(dx)^2 + d^2(T)/(dy)^2+ d^2(T)/(dz)^2

Is anyone has experience in solving this kind of problems? Any suggestions on how to deal with Laplacian term using VUMAT are appriciated.