I tried to open the capx but dropbox says it can't find it (yes, I took out the ...).
My prior explanation only works if your using a set background image and scrolling downward. If your making a true infinite jumper then you will need to measure the height of jumps and add them to a variable that is shown as total height jumped. But the idea is basically the same. You grab current Y when jump is pressed and the max Y when falling animation kicks in or you land. Then you can take the difference and add it to a height variable to post.
The thread I linked to has all the code you just need to remember your using Y and not X values... and your going up so Y values will be subtracting...