ActionScript 3.0 :: Clickable/unlcickable Stacked Objects?

i'm trying to develop a simple isometric flash game using AS3, but i have run into a small problem.

let's say i create a new movieclip (let's call it "ground") for the terrain base hexes (the ones that the character stands on) and populate that with more movieclip objects that represent each of the squares.since i want the game to be mouse-based, i want these hexes/movieclips to be clickable.

now, i will create a new movieclip (let's call it "objects") on top of the previous one that holds all the objects in a given map + your character and all the monsters. i want to do this, because then i can arrange the order (the z-depth) of the sprites according to their position on the map using swapChildren, etc (so that if your character is in a row in front of a tree, he is displayed on top, but if in a row behind the tree, he is displayed behind)

since the trees (or whatever other objects) can have clickable hexes behind them, i don't want them to get in the way of the mouse being able to detect the hexes themselves. the easiest way would be to make them mouseEnabled = false. but that would mean that i also have to make the whole "objects" clip mouseEnabled = false. at the same time if there are monsters inside the same "objects" movieclip i would want them to be clickable (for example to attack them), which means i cannot make "objects" mousEnabled = false.

hence my question. you can only change the depths of movieclips using swapChildren if they are in the same parent container, but you cannot make only part of that container's child movieclips invisible to the mouse. am i understanding something wrong and there is a different way to do this, or is this an actual and un-overcomeable limitation of AS3?