Assembly Programming Question

Hello, I am trying to write an assembly program. In it I am writing a new ISR for the keyboard. The goal of this ISR is to mix the keys around, so for example if I was going to type 'hello' It would print out as 'jhwwi'. It will only change the letters around so if there is something else in the input, such as a number, it will jump to the old ISR.

I have spent hours on trying to figure out how to accept input from the keyboard so that I can decide if I have to jump to the old ISR or use xlat on the mapping table I have. I tried using int 16 ah = 05 and int 16 ah = 10 but it doesn't seem to be doing anything.

This is about the only thing that is stopping me from completing this program because without getting any input from the keyboard I can't really do anything with it.

Thanks,
james