Wow! That were some fast answers.
Thank you! It works now.

If you have to write "on_u" in the main function. Does that mean that you can call functions via your keyboard only from within a function/main function? If so, could you just write a function that includes all on_key lines and call this function from the main function?
Something like

function main()
{
...code...
call hotkeys;
}

function hotkey()
{
on_a = ...;
on_b = ...;
etc...
}

again, thanks for helping
(hope you don't mind these basic questions)