How to connect 2 dvi cables together

I have a bunch of 6ft dvi cables and need one 10ft dvi or longer, a 6ft cable is not longer enough. Im sure its cheaper to buy an adapter or attachment to the cable then buying a new one. What type do I need to connect 2 6ft dvi cables together?

Thanks

I don't know if those adapters exist or are easily found because 15ft length is the max according to the standard (although you can go longer if you are using lower resolutions). You might need to look into a DVI Amplifier.

Monoprice has DVI cables that aren't that expensive with the appropriate length.