CFD Online Discussion Forums - Robin boundary condition containing two dependent variables

Dear Fellows

I know how to implement Robin boundary condition for a dependent variable

in OpenFoam using swak4Foam. For instance, the boundary condition:

$k \frac{\partial T}{\partial n} + \alpha T = \alpha T_\infty$
can be written using swak4Foam library as described in the following link:

http://www.modlab.lv/docs/2011/OpenF...Vilums_pdf.pdf

However, my question is if my boundary was in the following form:
$\frac{\partial T}{\partial n} + \frac{\partial \varphi}{\partial n} T = 1$

in which both

and $\varphi$ are dependent variables. How can I implement it in OpenFoam?

I am thinking of using codedFixedValue option for this boundary condition.

Any hint is appreciated.