APC UPS cable extension?

[Rutger]

I would like to extend my signal/data cable from my APC UPS to my pc to 10/15 meters.
This 10-pins RJ45 to usb connector cable is now around 2 meters long. In the RJ45 connector only 4 pins are used, the rest is empty.
I know that you can extend an usb cable to 5 meters, maybe more with a powered USB hub.

I tried it already with an UTP cable, but I saw later that the RJ45 was 10-pins instead of 8

Are there other options or cheap ideas?
I don't want to use an expensive usb over ethernet connector or what so ever.

[Akatar]

cheaper then this??

http://dx.com/p/usb-cable-via-rj45-exte ... air-123484

[Rutger]

I can't build that for that amount of money, I'll give it a try.