Welcome to the forum.
If the movie is to big to fit to a std DVDR disk, then it has to be re-encoded to a slightly lower bitrate (hence a smaller file), re-authored and burnt. Have a read of this tut, its intended for DivX to DVDR but load the dvd ifo file in instead.
http://club.cdfreaks.com/showthread....threadid=61142
Then there is the program
dvdxcopy from 321 Studios (see advert above), iI havent tried it yet but it appears it can split a large DVD to fit to 2 DVDR's.