Macro to set Wall Shear Stress

Satish

hi

can anyone help me in writing a udf to set the wall shear stress as below

Wall Shear Stress = (5/16)*(density*sqrt(2*pi*R*T))*((3/4)*(viscosity/density*temp)*dt/dxw)

Heat Flux = sqrt(2*pi*R*T)*C*(5*density*Cp/16)*(Tw - Tg)

here i need to write this in DEFINE_ADJUST as i need to update the value for every iteration. I know the macros for all the terms in the above eqn. except the wall shear stress and heat flux. Can any one help me in this

dt/dxw = derivative of temperature wrt x at the wall

Thanks

Satish