mouse position not working while dragging with left mouse button

sorry to bother you again, but i am not getting any further myself :frowning:
the most bootom object in my inventory_hud is the canvas object.
how can i apply the onDragover to it or do i have to apply it to the invetory objects ?
i cant find a ondragover function at all ???
please could you explain this again a little more detailed to me ?
thx very much in advance
kind regards
stucki