Problem joining three avi files at audio streams

[MoonWalker]

Hi. I have a problem joining 3 avi files I had cut with vdubmod..I open the first, append the second, and when i try to append the third one it sais :"cannot append. Sampling rate error (7000.00000 vs 6999.00000)"..How can I join these files?

Thanks in advance,
MoonWalker