[MacDV] more than one "session" on a DVD-R?

[Timothy Luoma]

I have a Powerbook w/ Superdrive (not the newest one).

Whenever I make a DVD through Finder, it seems to make it so that I 
cannot add anything more to it later (i.e. if I only put 1GB on there 
I'd like to be able to put another 3GB on there later).

Is there a setting I need to do with this, or is this something I have 
to use Toast for, or am I missing something?

Thanks

TjL