C-c C-c for a file extension

[Rares Vernica]

Hi,

How can I define a C-c C-c command for a certain file extension.

For example, I have the gnuplot (.plt) file and I would like to run 
"gnuplot %f" (where %f is the file name) when I press C-c C-c on that file.

Thanks a lot,
Ray