Variable frequency interrupter code?

[FilipSebik]

Hey, I am done building my SSTC, but there is 1 thing I am missing. Its the interrupter. I would like to have one that can do 50Hz - 20KHz but I don't know *@#! about arduino timers or something to change its frequency. The duty cycle would be 50% at all the time and the frequency should be variable between 50Hz - 20KHz through a 10K multi turn pot. I have Arduino Nano and Attiny85. I would like to use the Attiny85 because it would save space and less expensive to replace. As far as I got, I have no code... Any help would be appreciated

PS: Yeah I know I am asking someone to do it for me but I just can't understand what does the TCCRB = 0; means and other things