Not that we support VBox here, but because I use the same thing when I can't be bothered to reboot, I'll give you a hand.
When you boot your VirtualBox, there are icons on the bottom right of the statusbar. Click the one that looks like a USB end, and select your USB WiFi stick from the list. VBox will then pass it through to BT4, and you'll be able to use it in BT4.




