How to solve PDE in comsol

Hi comsol support team

                                     I am mani Shankar yadav research intern from IIT Ropar India. I am facing problem while solving PDE solution in comsol. 

be expressed by the following continuity equation: ∂nD/∂t= ∇⋅(D∇nD- vnD+DSnD∇T )

Here, nD is the n suffix D.

In this equation how to introduce third term (DSnD∇T) at right hand side in order to solve PDE equation.