I’ve spent 30 minutes playing around with AE trying to get this effect for you and you’re right: there’s no easy way to do this.
One possible option – and it seems a bit of a long way round but…
You could pre-comp your text animation so that it animates down, then track the cursor so you can use it’s Y value to animate the position of your pre-comp. That way the cursor can move left-to-right, but as it moves down, your pre-comp will move up. Your cursor will stay in the same position vertically.
http://www.YouTube.com/ShiveringCactus – Free FX for amateur films
https://shiveringcactus.wordpress.com/ – FX blog