Powershell script to move DB Users to an AD Security Group

I need to write a powershell script that will move users that mailboxes are on a certain database from one AD Security group to another group:

For Example

Users mailboxes on Storage Group 1/DB1 are in the AD Group Clust1 and need to be removed from Clust1 and added to the group Clust01

Im guessing i would need to use a combination of get-mailbox -database datbasename and probably something like add-adgroupmember sourcegroupname but not sure how to combine them.  havent had to do much powershell scripting in the past!

Many Thanks

Dave