RenewCommand , Change text of Part I, Part II, Part III

[Marcelo Reis]

Guys I'd like to know how to change the Part I , Part II, Part III to 
any text I want (like CHAPTER , or whenever I need)
I could use the environment with *, but this way it would not appear in 
the TOC.
I also need the words Part I, II....centralized.

Thank you so much, as usual.
Marcelo