Trial membership upon registration

[truckworks]

I posted this question here, and also found a few search results related to what I'm trying to do. 
 
One from 2008 
 
and another from 2010 
 
Here is what I'm trying to do: 
 
- Guest decides to register, goes through process
- Upon registration, member is automatically assigned to "Trial Member" membergroup
- Trial period lasts 3 weeks, then member is reverted back to guest status without ability to just keep renewing trial

I attempted to do this via paid subscription (set cost to $0.00, but PayPal kicked it back) and didn't see any potential solutions in the permissions area.     
 
edit: Apparently "revert to guest status" was a poor choice of wording.  Perhaps I should have said "switch to a default membergroup" instead.

[margarett]

I don't get it... You want to kill each member every 3 weeks? Because you have to remove the account to make it a guest again...

[truckworks]

After 3 weeks they are removed from the membergroup and set back to a basic, limited status.   
 

[Kindred]

ah, but that's not what you said... you said " reverted back to guest status"
(which is, essentially, deleting the account)

[truckworks]

Just seems like splitting hairs to me since I've got multiple avenues of controlling what they can/can't see AFTER they're booted from the trial group.  Doesn't matter either way, the only important thing is filing them into a membergroup automatically upon registration that can be time limited. 
 
edit: nvm, I see what you're saying now.  Thanks for the response.

[margarett]

I can only give you an insight on how I would do it because I'm seriously out of time right now:
There is a MOD already to automatically add members to a certain group at registration
http://custom.simplemachines.org/mods/index.php?mod=1804

For the "3 weeks" thing, you can run a scheduled task that picks the users belonging to such membergroup and, if their registration date is <= 3 weeks from time(), set primary group = 0

This is plain simple if you are using primary membergroup. If you want to go to additional membergroups (to keep the status hidden), then it's *MUCH* more difficult.

Good luck

[truckworks]

Alright, so looking at that mod is there a way to change it so you can automatically assign people to a paid subscription instead of a membergroup?

[margarett]

Dunno, you need to ask in the MOD's support topic http://www.simplemachines.org/community/index.php?topic=308635.0