Subject: Re: TradeTriggers@TDA; INTRADAY % price drops
PS I think this is the IB syntax to build an example of the order you want:

< BUY IF FALLS 1.65 % FROM CLOSE:
'Percentage Change of IWM STK on Smart is < [LESS THAN] = '1.65 %'' means if stock declines from close a greater amount than 1.65 %' then BUY.>

There are options for entering the type of order [e.g., snap to bid, ask, midpoint; various limit variants; even -YUK- market; & more] you want when triggered, too.