How can I catch a keyboard input and return another character to Framemaker?

Hi,

I want to catch an keyboard input and return another character to Framemaker, like e.g. changing a "y" I type into my computer into a "z" and vice versa or changing the arrow key "right" into "Tab".

For me, the biggest issue in this is to find a solution to catch the keyboard input by ExtendScript for further processing. I tried the Notify-function, but it doesn't seem to work like described in the Scripting Guide and I have no idea how to make it work. I hope that someone here knows a solution for at least the keyboard input issue.

Thank you in advance.