drag drop - change [cursorAt] while dragging

drag drop - change [cursorAt] while dragging

Hi,
 
I have two droppables shown once an item is dragged from the page. One dropable is shown on the left-top of the screen and other is shown on the right-top of the screen. Now, the problem is [cursorAt] property. I want to change this property dynamically when user is dragging an item on the page. If dragging goes more than 50% right to the screen then change the [cursorAt] property so some what {right: -20, bottom: -2}, whereas if dragging goes more than 50% left of the screen then again change [cursorAt].
 
Please help me to solve this problem
 
Thanks in advance,
Bhavnik