Controlling VirtualBox Guest Actions

On the Guest:
vboxcontrol guestproperty set TestState ready
vboxcontrol guestproperty wait foo
"C:\Program Files\Windows Media Player\wmplayer.exe" /prefetch:1

On the Host:
#!/bin/bash

retVal=0
retVal=`VBoxManage guestproperty get WinXp TestState | grep Value | cut -f 2 -d \ `
echo $retVal
while [ $retVal != ready ]; do
echo foo
sleep 1
retVal=`VBoxManage guestproperty get WinXp TestState | grep Value | cut -f 2 -d \ `
done

VBoxManage guestproperty set WinXp foo 1