[R-sig-dyn-mod] How to change a parameter after steady?

Hi there,

I have established a model. I set the times to a enough long period, so 
that the model runs into steady state. After the model reaching steady, 
I hope to change a or several parameters and run the model for a fixed 
periods. I expect to see some changes of state variables or auxiliary 
variables.

How to implement it? Thanks a lot!

Best wishes,
Jinsong