I have been using time dependent boundary conditions by inserting the required function with respect to variable t in the Dirichlet or Robin conditions at the required boundaries. I guess that's obvious so maybe you don't mean that? It is not clear what is the problem where you are stuck.
The simulator was producing an error when using time dependent boundary conditions. I was not sure if I was setting it up correctly. It looks like it was a bug in the simulator, so the issue has been move to the Technical Issues forum.