Change parameters in pcDefinePCell code body

Hi, I have a normal pcell that you can give certain parameters.  I want to check in this pcell if certain parameters are between a min and max value, and the reset the parameter to this value.  How is this done?

For now i tried a if else statement.
So I have parameter l, in the code body i check

if( l<minL then l = minL)

If I create an instance of this pcell, and enter a value lower as minL, this results in a pcell with correct l, only the value I initial entered is still visible in the instance parameters. 

Can I change this?

Thanks,

Rik