Assign a key code to Fn+F3 combination

[bizooon]

I have the Asus A6Je laptop. When I press Fn+F2, keycode 246 if fired while F2 alone fires keycode 68. When I press F3 or Fn+F3, keycode 69 is fired. I would like to change the keycode fired for Fn+F3. Is it possible to do this in Gnome?

I am using Main edition 10 - Julia.