how can i solve a differential equation with two independed variable?

 so I have this function : c(x,t),
and I want to solve 
∂C/∂t=D/(1-(1-M)C) [∇^2 C+((1-M)〖(∇C)〗^2)/(1-(1-M)C)-(qE_ext)/KT ∇C]

Im getting this error: "Symbolic ODEs must have exactly one independent variable"

what is the best way to solve this equation?

thank you all.

[Torsten]

Try "pdepe".

Best wishes

Torsten.