Actionscript 3 :: Setting Multiple Depth Layers?

I get how to set depth in as3 - but with as2 i could begin multiple 'depth points' using numbers - where in as3 all i can seem to do is set this object to a higher/lower depth than that object. The problem is (when dealing with a stack of isometric boxes, which can be placed by the user on a grid in any order) i don't want to deal with the added complexity of having every element know where every other element is, then adjust appropriately.

What I'm trying to do is set up 6 total depth numbers/positions, one for each column in a 6 x 6 grid. So anything in column 1 will begin it's depth placement at say 500, anything in column 2 will begin its depth at 1000, column 3 would be 1500 and so on.

That way, the second i place an object on a particular column, it would tuck itself under, or place itself above all surrounding items in other columns, this to me is much much easier than somehow figuring out where 15 different sized boxes are, how they relate to one another, then figure out what depth order they need to go in. as3 seems to have removed the ability to set a depth to a specific number.