I'm pretty sure there is a limit in length of the standard 15pin Dsub which monitors use, lots to do with syncronising and degradation. You may get above 2m (6.5'), you may not. What I would suggest (and have done myself) is to use TVout on the gfx card, run this to my VCR which my monitor sits on which can take VideoIn/SCART (also limited in length) and output through a standard RF (TV set) lead which can run 15m+ (about 50'), hardly the highest quality solution but excellent for viewing movies etc on my big screen TV in my livingroom while keeping my PC in my bedroom. HTH.
You can get cable extensions from most electronic stores that carry computer accessories. You can also get them at most online stores too. I got mine off of ebay for $7-8 shipped. Pretty cheap in my opinion. But again, the longer the cable you extend...the more distortion you're going to get on your monitor. My cable was about 6' long I believe. When I plugged it into my Princeton 19" monitor, the picture was distorted and wavy. But when I plugged it into my old 14" monitor, it didn't seem to have any problems. Of course, I'm running at a much lower resolution too. I wouldn't plan on using this on a main monitor that you would use all the time, but would be useful for a 2nd monitor for an old linux box or file server.
Here's one from Amazon for about $5 + shipping. link