Add time to active members of an entire subscription?

[sub_ubi]

Had a problem with a section on my forums, and would like to give all active members of this particular subscription id a free month.

Any way to do this? I have full phpmyadmin access if that makes things easier.

--------------- Added [DATE]1229649804[/DATE] at [TIME]1229649804[/TIME] ---------------

Would something like this work?

UPDATE subscriptionlog
SET expirydate = expirydate + X
WHERE subscriptionid = Y