partial derivative of external MATLAB function

Hi,

I am modeling reactive transport in COMSOL and have external MATLAB function to solve the chemical reactions. MATLAB function is defined based on five COMSOL variables as follows;

FUNCTION NAME: r_kin
ARGUMENTS: u1,u2,u3,u4,u5

External MATLAB function works properly but I want to define function derivative. May anyone like to guide how to define the partial derivative of the above stated external MATLAB function.

Regards,

Nawaz Ahmad