A* Pathfinding in Flash

Hey guys,
I'm trying to write an A* pathfinding code in actionscript 3 and i am now stuck on working out the distance (in tiles) between the two targets.

I'm trying to use this tutorial
http://www.policyalmanac.org/games/aStarTutorial.htm
and am at the path scoring bit, and i am now totally stuck.
Any idea how i can work it out?

The map is split into tiles and is 8 by 8.

Any help or anything would be greatly appreciated

Thanks,
Blade

Mwhaha i managed to figure it out eventually
Still got a long way to go though