Problem to synch audio and video with diferent framerates

[totoro]

I work on a movie (manga) which i've got 2 sources : 1 avi divx movie with original language encoded in 23.976 FPS (NTSC) and good video quality ; and another file (from the same movie) with French language in 25 FPS divx format (PAL) and poor video quality.
I would like to mux the french language of the second file with the good video quality of the first file. But the framerate is diferent, and I can't mux them (I going to make me mad).
I tryed to adjust the interleaving setting in virtualdub before muxing, but it didn't work.
How can I do that ? Is there specific tools to mux 2 diferent framerate files ?
Or should I modify the framerate of the 23.976 FPS avi file to transform it in 25 FPS ? How can I do that ?
Thanx a lot for your help
Best regards
Totoro

[Belgabor]

Sound has nothing to do with framerate. What did you exactly do to mux? Usually you would demux french audio (detaching it from anything where fps matter) and mux it with your video. If by 'can't mux' you mean its out of sync you can try 'Video -> Frame Rate -> Change so video and audio durations match'. If that doesnt work you'll have to change the sapling frequecy of the audio so both match, a lot of trial and error, I'm afraid.