boundary condition dependent on dependent variable

Hello everybody,

In a coupled heat and mass transfer problem, I would like a pressure BC to get updated at each time step. Let's call this pressure pv.
pv depends on the temperature and pressure (dependent variables solved for in the problem) and the value of pv at the previous time step.

Does anyone have an idea how to implement that in Comsol? Using Matlab is an option.

Thanks a lot for help,