I have a managed form with an "universal" inputfield and want to do same action if user press key on keyboard.

On every key pressed i want to examine the keycode. If it is a valid input the key is add to the inputfield, if functionkey
is pressed i want to do same action.

Can anybody help?

What kind of task you want solved? Can you give an example?

You can use Keyboard shortcuts for commands to add functional buttons to your form.