Add pointer Up / Down at runtime (Button UI 4.6)

Hi all !

There is my problem :
I would add to my buttons, the Pointer Down and Pointer Up at runtime,
then, add them the GameObject and Script by script (see the pic)

2 days i try lot of things, and nothing :/
So, many thanks in advance for your answers :)

(little precisions : I use JS, not C#)