syncronizing ac3 track to a video

[jv_guano]

A dvd that I am has not my native language's audio, so I'd like to add it

All kinda of demuxing and remuxing are OK to me, the only problem is how to syncronize the two streams?
I cannot add or remove some milliseconds and remux everything again, it's a waste of time..

Is there a way to pre-load video&audio streams in a program like VDub, adjusting the two streams so to find the amount of milliseconds to set up in IfoEdit?

Thanks a lot!!

EDIT: okay, I'm a dumb! :D
I can openm the video stream with VirtualDubMod, and then on Streams->stream list, choose "add" and add my ac3 audio stream...

but I cannot hear the audio!!! :( :( :confused: why?
I also installed this AC3 Filter (http://ac3filter.sourceforge.net/#download) cos on a guide there was written I remind you that to play correctly the AC3 audio track, you must have installed the proper DirectShow filter (AC3 Filter Downmix). You can donwload it from here [the link I write before that quote]
I also closed and reopened VirtualDubMod to be 100% sure, I reopened the vid&audio streams, but nothing.... :( :(

please, help me!
thanks!