Need to lock volume rocker switch on Samsung Galaxy S III while playing Spotify music

[user-removed]

I have found Android apps for the Samsung Galaxy S III that lock the physical volume rocker button on the side of the device and they work when not running Spotify.    BUT ... when running and playing music in Spotify, the app does not control the volume rocker like I wish.  I want to lock the volume of my Spotify music so that I don't accidently change the volume when I put the device in my pocket.  Anyone know of a volume locker app that works for Spotify volume?