Changing from nmos type to nmos_dnw type ALL NMOS transistors of ALL cells in same library with SKILL?

Dear all,

I need to change all the NMOS transistors of every cell in the same library from a type nmos to a type nmos_dnw, leaving the rest of properties unchanged. (Hundreds of cells)

How do I start? Is there any way to "record" a macro of actions with a single cell, and run it over and over selecting different cell?

Any help is appreciated.

Thank you

Cheers