I would also like to be able to play the previous track and play/pause. The problem is my keyboard doesn't have multimedia keys, so I want to setup hotkeys to do the same thing.
As described here, you can create a powershell script which gets called by a batch file:
$wshShell = new-object -com wscript.shell $wshShell.SendKeys([char]176)
powershell -ExecutionPolicy RemoteSigned -File "C:\path\to\your\script.ps1"
There's also a list of other keys:
Volume Down: 174
Volume Up: 175
Next Track: 176
Previous Track: 177
Stop Media: 178
Your best bet would be to use Autohotkey as this allows you to map keyboard shortcuts for most programs.