Add piezo-resistive coefficient in doped channel for MOSFET

Hi,

I am simulating the Ids current in a MOSFET. I want to see the Ids current change on application of mechanical stress. For that, I wanted to add the π-44 piezo-resistive coefficient of the doped channel region...

How do I change the property of just that region? And should adding this region property help to see variations in Ids with stress?

Thank you very much..