how to drop element on overlapping element

how to drop element on overlapping element

I am using drag and drop functionality in my site so that i can able to place any div at any place. and i can able to drop image to any div , its working fine . the problem i am facing is whenever any div over lapping with other div while dragging and drop any image to the overlapped div then the image is droping into the down div not the above div , i am unable to find the droped div id ,

If any body faced such problem let me know the solution 

Thanks in advance
Surya