Like AG states, it's far cheaper and likely more reliable to simply buy the cable than to build one. What you apparently need is what is pictured below. They are available at most larger department stores, Radio Shack, Best Buy, Circuit City, or similar types stores that may exist where you live. Where do you live? Doesn't matter since you can order one via mail order distributers. You need a STEREO 3.5mm mini-plug to (2) RCA Plugs and they come in typical lengths of 6', 12', 25'.
**broken link removed**