Backtested results from historical file

I am using the code from the page -

http://www.amibroker.com/kb/2014/09/30/gen-backtest-from-a-file/

I am unable to add to an existing position using this code. The only trade listed in the Amibroker results is 10/16/2000 with 21 shares. If I try to add to the position as in 10/17/2000 Amibroker ignores this trade. I am missing some configuration parameter in Amibroker to allow the added position?

Input file looks like this:
Symbol,Trade,Date,Price,Shares
ADP,Buy,10/16/2000,47.8317,21
ADP,Buy,10/17/2000,47.5343,42
ADP,Sell,10/20/2000,49.6656,63

Thanks for any help/direction.

The formula from KB does not implement scaling-in. Second buy is redundant (because the position is already open) and as such skipped.

Hello, how can we implement scaling in in the formula? I use this formula a lot, thank you

http://www.amibroker.com/guide/h_pyramid.html