how to observe the transistor dimension variation in monte carlo simulation

 Hello,

      I know that people can observe some transistor parameter changes during the monte carlo simulation, but there is no options to let user choose width or length of a transistor as a observed parameter, what's your method?

by the way, my approach is to build an expression including some parameters picked up by "opt" in calculator, but the transistor size is not there.

generally, are all the transistors in a circuit applied the same variation in a simulation? or each transistor has its own variation in the simulation? I noticed that some people mentioned one model card and multiple model card, is this related to the transistor dimension variation?

regards,

zfeng