Can I change the update schedule of multiple collections, i.e. with Powershell?

Dear all,

I have about 500 collections (user and device) with different update schedules (ranging from every 5 minutes to never at all) and now wish to change the update schedule to a general one (once every 30 minutes). I know how to set the schedule with Powershell, but only when creating new collections (New-CMUserCollection ... -RefreshSchedule...). Ideally, I would put all my existing collections in a text-file and run an appropriate cmdlet to adjust their schedule, but unfortunately I do not know which one; Set-CMUserCollection i.e. does not accept the parameter -RefreshSchedule.

Does anyone have an idea how this can be accomplished without having to touch each collection manually?

Thanks in advance

Lars Bremer