Change the ton of a REX file

Hello,
Sorry for my english, I am french... ;-)
I am using Sonar X1.
I have bought REX files for guitares or basses for exemple...
I have a question. When I have a REX file, it can be in C tone. OK.
Is it possible to change this tone in G ?
Because I have try to change the height and the result is so bad to hear...
 
Thank you very much,
Nicolas