gamma panel for brightness and contrast adjusting

Sorry if I post this on a wrong section.
But I do hope if you can help me on adjusting brightness and contrast.
In fact I want to write a little progam to change my display brightness and contrast, just like what you can do in your nVidia or ATI control panel.
But I really want to get much more control than that.
So if you will be kindly let me know how I can fulfill this ?
Please tell me how if you knows even a little....
Thanks.....