Add subscribers manually?

[Marit]

Is there a way to add a subscriber manually in admin? I have added a subscription forum on my board (pay with Paypal) and some users would like to subscripe by using other means of payment. I know I can just change their usergroup and give them access that way, but that sort of defeats the whole point as I would have to keep track of whose subscription runs out at what time. I have looked around in admin, but could only find how to add new subscriptions, not new subscribers to an already existing subscription.

TIA!