How to create layout xl for user defined pcell with same parameters as in schematic??

Hi ,

I need to create a layout using layout xl. The thing is i need to get the parameters as in schematic for pcells in layout. 

Example:- 
nmos has a schematic and layout. Now i created a pcell with this nmos like nmos_esd with two parameters length and width. And copied nmos schematic and renamed to nmos_esd.

But when i tried using "generate instance from source" option in layout xl. I am getting corresponding nmos_esd. But the parameters are default and i cant able to edit. Is there any way to map user defined pcell parameters?? Please help..


Thanks & Regards

Karthik.