The VirtualDub_Sync Version that bb meant you can find here:
http://www-user.rhrk.uni-kl.de/~dittrich/sync/
But it will give you drops to get sync, so your video and audio are sync in the end but depending on your source sometimes many drops, but for me this version works fine, I am sorry it has no Timer, as bb said already.
To get Video and audio sync in "normal" VDub you have two options:
1. The best is to get it sync during recording:
in VirtualDub Capture mode you choose capture -> Timing -> enable "adjust..." Thats it
2. If you forgot this, or if you have asynch movies on your Harddisk, just open it in VDub, set Video -> Frame Rate -> enable "Change so audio and video.." That will give you a new frame rate (i.g. 24.9876 not 25 PAL) and your movies gets sync.
If you want to know more about drops, you can
on the top of this site.