sorry Mat I replied to early, in the scripting forum there is a script for using gann swings to find a certain percentage retracement ie,
This is a way to scan by using variables such as Gann swing to find retrements, scanning etc, The one the google search point to is the manual application of very specific rules.
My recollection was that there was a script on the forum using similar variables to the gann swing retracement but to find extensions of range.