How to do parametric analysis in maestro

Hi,

I am trying to do parametric analysis on width of pmos by following steps

1. First i created a circuit using Ipar parameter

2. Created symbol and passed the parameters in CDF

Now I am using the the symbol to create new test bench and passing the parameters in maestro by selecting parameters of symbol passed in properties section . But I am getting following error

myckt.mpo effective width is off grid 1e-7(myckt is symbol instance name)

I am giving parametric range like 200n to 300n with 20 steps.

Thanks,

Manoj