how to fix a cruise control button in my car?

I have vauxhall vectra, TDI 2.0L LS hatchback, year of production 2002, It is fitted wit the cruise conrol switcher. It doesn't work any more. This problem appeared a couple of years ago for the first time. Since then it has been or hasn't been working in turns. Currently it doesn't work at all. I checked the fuse and it's ok.
Thanks for help