Amibroker 20 percent flipper strategy

Hi everyone,



I have just started to learn and look into Amibroker to create a trading strategy that would suit me. I have read about the "20% flipper" strategy that sends a buy signal when a stock has bounced off a low by moving 20%.



I don't know how to write this in AFL language so I am wondering if anyone has done this before and to help me with some code?



I know how to do an index filter and size positioning but I just don't know the array that will help measure this 20 percent change of a particular low or reversal in price.



Thanks for your help in advance



Phil