when a sensor moves over some other object

[durf]

Hello,

Still kind of new to python language.

Lets say I have a "white_ball.wrl"(ball) that is linked to a ppt sensor. And I have a block that is located at position (10,0,0). What I want to happen is if the ball moves over to position (10,0,0) the block will have a new set position at (10,-10,0). The ball can be at any level on the y-axis by the way. I only want to worry about where the ball is on the x and z axis.

What I need to know:

What do I have to do to compare the position of the ball == to the position of the block(keeping in mind that there is a surface area on the block of unknown size.)?

After it compares the two to see if the ball is over the area of the block, how do I set the position of the block.

Any help will be much appreciated.
Thank You