Mass lock/unlock of user ID's

Hi

We have to lock 50 000 + users when maintenance needs to be done on the system.

Currently using su10 or EWZ5 takes more than an hour to lock and or unlock the users.

Is there a quicker way to get the users locked. Is anyone doing this programmatically ?

What are the pitfalls when writing an ABAP just to change the user flag on USR02?

Thnx

BRian