@notebook-I used keyboard's chip and (sry I lack expressions in english) clean board for making electronics..Download some program for testing keyboard and then you must find what combinations are letters you need made of..Then you just weld switches and make a box..
@smarly- Ctrl,Alt,Gear,trim and shift buttons are ON when needed and rest of them are switches that turn them self back after beeing pressed..Trim and Shift are having 3 positions..in middle is off down is pgdown and up pg up same for shift buttons..