I've got a wireless keyboard that puts some media keys on top of the Function keys, so that by default F4 is actually lock (Rwin & l) and Fn+F4 is a real F4. So I'd like to basically switch those around. Here's what the key history shows:

VK  SC  Type    Up/Dn   Elapsed Key
-------------------------------------
73  03E         d       17.32   F4              ; Fn+F4
73  03E         u       0.16    F4              
5C  15C         d       2.96    Right Windows   ; F4
4C  026         d       0.00    L               
5C  15C         u       0.13    Right Windows   
4C  026         u       0.00    L            

This doesn't do anything:

SC15C & SC026::MsgBox,Pressed F4

But this prints that I hit F4 then goes to the login screen:

Rwin & l::MsgBox,Pressed F4

So how can I stop it from switching to the login screen? Ideally I'd like F4 (which registers as Rwin & l) to just send F4, Fn+F4 to send Rwin & l, and also have them work with other keys (e.g., a manual !F4 should still close a window). Is this possible?