How can I make the hotkeys work?

[donovan]

When I play music with Windows Media Player while browsing the internet, pressing Fn and the arrow stops my music.
I have configured foobar2000 and VLC to use this hotkey.
But it only works when foobar2000 or VLC is on the foreground, not when it's playing music in the background.
How can I make it work when I am browsing the internet and my music player is working in the background?

Many thanks