This whole series of tutorials is slightly obsolete because BYOB has been replaced by Snap! (http://snap.berkeley.edu) but the ideas are still right.
This is the first in a series of tutorials about BYOB 3. This one is about how to use first class procedures to build a tool procedure, namely a FOR loop that can be used in other projects. This tutorial runs in Scratch 1.4, but the actual FOR loop runs only in BYOB. This is the first part of a two-part tutorial, because the whole thing is too big to upload to the Scratch site. After watching this half, you can find the other half at http://scratch.mit.edu/projects/bharvey/1011149 Or you can download the entire 20-minute tutorial at http://byob.berkeley.edu/BYOB3-tutorial1.sb