Software Simulation: Move slide when keystroke typed

Hi all, I'm hoping you can help me out with a technical consideration with Storyline 2. I'm doing a software simulation course, and I need to mimic the behaviour of an application in the 'Try Me' section of the elearning course.

On the application that's the subject of the training, if a user clicks in a field and types, say, MEX, as they type, they see a list of results which filters down as they type more characters. To mimic this in the elearning, what I need to happen is that when the user types the letter M, the elearning moves to the next slide, then when they types the letter E, it moves to the next slide, and finally when they type the letter X it will move to the final slide.

The problem with Storyline is that I can only get it to move to the next slide when the text box control loses focus. In other words, a learner would need to type M, then click outside the text box, then click back in the text box (on the next slide), then type E, then click back outside the text box and so on. Which doesn't replicate the application behaviour. I know it's possible to get it to work the way I want in Captivate, but I can't figure out how to do it in Storyline. Does anyone know of any clever tricks I could employ? Perhaps there's a way to force the text box control to lose focus after a character is typed in?

Any/all ideas welcome!