ya you cant control mouse but you got a way
its simple
1.make a fake pointer is a MC that look just like a mouse pointer
2.hide the mouse using Mouse.hide();
3.now you are free to do whatever you want with fake pointer

innt it simple !! ;)

I'de like to move the mouse(cursor) position up in the y-axis (by say - 30 pixels) each time the mouse is clicked.

you can't control the mouse with actionscript. you can create a custom cursor
and you can control that using actionscript.

but it still wouldn't make sense to alter the cursor's position as you're
describing unless you want to aggrevate users.