Automatic program removal

I work for a school district, and the users have downloaded a program that allows them to spruceup there outlook bar. It appears to be affecting the way that outlook responds and is slowering down my exchange server. I would like to remove it automatically via my network, through some type of group policy or login script, etc… in such a way that it is totally transperent to them and will not allow them or anyone else to install it again. I hope someone can help, I would really appreciate it.