How to write 3 movies in one dvd thru Nero?

hi all...need to clear a doubt.....i am writting my downloaded movies (AVI format) into DVD thru NERO Ver 7. some times when it converts it shows 4 GB that makes my disc full with one movie. i need to write atleast 3 movies in one DVD...Is it possible to do like that in NERO or i want to use another software for writting those movies...

Anybody knows the answer please help.....

Thanks