Listen for the Frame Number and Display Current Frame

I have tried this a dozen different ways and I really am at my wits end.

I have a presentation that works like a powerpoint. Everything is working as it should, except one part. I have a movie clip with an instance named slides, and I want to actively display which frame number you are in this move clip.

I have tried more than one why but I see no reason why this should not work:

var frameNum:Number = this.slides.currentFrame;
this.frameText.text = “Páquina " + frameNum + " de 173”;

It appears to work at first, but does not update when I navigate the slides. It constantly says 1. Before I just added a function to the back and next buttons to frameNum++ and frameNum–, but after I created the Menu I would prefer it to automatically detect what frame it is on.

Some quick help would be much appreciated.