When reading stuff about min-max settings, be sure to note that it's often making reference to the "min-max" column in your style (.drt) file.

But that said, I'm also trying to understand exactly what you're doing before trying to offer a suggestion. From you you wrote, it sounds to me like you are measuring the RT to detect a change from one picture to another. But when I looked at your input file, I noticed you are repeating pic1 and pic2 over and over within the single trial. Is this intentional?