Payment Gateway Migration: Allow Current but No New

[crosswinds]

I am looking to migrate off of one payment Gateway and onto another. However, I need to allow the old Gateway to continue to allow existing payments to be billed, but not allow new charges on it.

Ideas on how to accomplish this? I cannot see to disallow new charges.

Thanks in advance.

[tallship]

I think perhaps one way you can tackle this is to create new, identical order pages for those products with the new gateway, and then 'hide' the old order pages.