New instances of the same window?

I want to be able to make a new instance of the same window. For example, in Text Edit, you can press +N to make a new document. I have already told my window to open on +N but how do I do the rest?

Model: iMac Intel
Browser: Camino
Operating System: Mac OS X (10.4)

Dear ihaveabellybutton,

I would suggest you, not to
create new instances, but use
Apple’s CoreData Management.

It is especially designed for
document-based applications.

Here are the movie tutorials,
it is really easy, you could finish in
just 10 minutes: