I don't think you will be able to bind the CNTL key to your mouse button as you want to do there. The in-game mapping doesn't have a spot for mapping CNTL.
If you got yourself a logitech mouse, you would be able to map Mouse 3 to CNTL easily using the mouse button mapping software.
I use the G300 and love it. The extra crown buttons are ideal.
http://www.amazon.com/s/?ie=UTF8&keywords=logitech+g300+gaming+mouse&tag=googhydr-20&index=aps&hvadid=31608670357&hvpos=1t1&hvexid=&hvnetw=g&hvrand=11680291651864663348&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_9hw4hprt0r_b
Sorry to suggest a purchase rather than an in-game fix. Hope this helps.