QT trader how to buy when price goes up past a certain point

[Galvin]

I was to make a rule that says buy when the sell price goes up.  So I'm at 600 resistance.  And I want to buy back in if the price goes past 600.   But I'm afraid with lag by the time the order goes thru it won't catch it.  Unless there is a way to buy below the buy price and the server will just use the current. I'm new to trading and I couldn't find any videos on how to use the rules.