parameterization the initial condition of a Switch/Breaker

Hi

I want to parametrise the initial condition of a Circuit breaker in Simulink like this:

But as I run the simulation the following error pops up:

Undefined function 'Masseknoten' for input arguments of type 'double'.

I have parametrized elements like resistors and so on, but it doesn't work for the initial status of the Switch/Breaker !!!

Any Ideas?

Thanks