User defined non-Newtonian models

Hi there,

I am trying to implement a non-Newtonian constitutive relation which is different than Carreau and power law in the CFD module. My viscosity model is a function of both shear rate (gamma dot) and the concentration ratio, hence has two independent variables! It also involves some constants and has it's own unique functional form.

Can anyone please tell me how to define this function and then how to call it for calculation of the viscosity for a non-Newtonian flow simulation?