Changing the FET model parameters dynamically during Transient Simulation

For example, I have some .scs file which has the following some generic model:

section typ
parameters
...
+ mainfet_rdsw = 5000
...
endsection typ

Now in the above model, lets say at some point of time during transient simulation I want to change that mainfet_rdsw to 7000, how can I do this?

I know I can list parameters to be changed in a file and use it as paramset=pset in "additional options" and I can change things like L,W or component values during transient, however; what I am trying to do is a little bit different thing and I wanted to know what should I do in that case?