[DanielCFD]

Dear foamers,
　
I am trying to add a user defined field depending on space and time (B(x,t)) to the Poisson's equation. It is not a source term! The Poisson's equation solver is part of a larger solver, like pisoFoam. First I hard coded it inside the Poisson's equation. But now I want to make it a bit more fancy and user friendly. I would like to have a file at the case level which defines the field. First, I was thinking I could use function objects but they seem to work only one way: given a calculated field one can perform all kinds of operations on it. But you cannot feed back information into the solver (Poisson's equation).
　
Any suggestion how to proceed?