Saveas AVI with changing extention

[Tomm]

Hi everybody,

Does anyone know how can I save an AVI file converted from a tiff file with changing file extension in macro command?
Here is my code.

dir = getDirectory("Choose Source Directory ");
filename = getTitle();
dotIndex = indexOf(filename, ".");
title = substring(filename, 0, dotIndex);
run("AVI... ", "compression=Uncompressed frame=3 save=???);

thank you,
Tom