change in pakage dependencies

Hi,

I'm maintaining the Debian Package for a network appliance. The Update 
is executed via Webinterface.
My problem is that I need an additional package in a newer Version of my 
appliance.

I can't change dependencies, that would lead to an error, right?
Do I have any chance to tell my new paket it needs package xy??

The User does not have shell nor console access.

Thanks a lot,

Jan U. Hartmann