Passing Array Variables In Functions?

What I am trying to do is to automatically build a "tree" diagram representing the links in a huge model which is dynamically configured. What I have a problem with is the following:

The tree consists of layers, I start off with the top layer and for each entry in the top layer I can add all its subsidiary layers and draw links between them, this uses a function which takes as its arguments the node name and its layer number (how far down the tree it is) and the number of items in that layer so far.

So I start at the first item in Layer 1 and there are as yet no layers below it. I start at the first one and add the first item in layer 2 then I kick the function off again and that adds the first item connected to item 1 in layer 2 in the layer below (3) starting at the first one, and so on. When I reach the bottom I go up one layer and add the second item in the bottom layer and so on. When I have added all the connctions to the first item in the next to bottom layer I go up one layer and add the second item connected to the first item in that layer and then add all the items connected to it and so on and so on.

In this way I build up the network exhaustively (to make things more complex more than one item in a layer may connect to the same item in the layer below).

I can do almost all that, the issue I am struggling with is I need to keep track of how many items there are in each layer (as some layer 1 items connect to 1, 2, 3 ...8 layer 2 items and so on). my idea is to keep a running total of these in an array LevelCount(1), LevelCount(2) etc. so when I add a new item to a layer I know where to put it. However I cant workout how to do this final step.

Currently I have a function that draws the nodes below a specified node this and takes the correct value from the array LevelCount(n) by passing Levelcount(n) (where n represents how far down the tree you are) into the function and the function then updates the value of LevelCount(n) (ByRef) so that next time I use it it is correct. That is fine but what I want to do is to is to call the same function from within itself when it adds each node which would make it work automatically - it would keep calling instances of the function until it reached bottom and then go back one step at a time to the top but I cant work out how to reference the right value in the array to pass into the second (and subsequent) instances of the function.

I don't think I can simply pass (n) into the function and in the body of the function set LevelCount(n) = LevelCount(n)+1

I also dont know ahead of time how many layers the model will have, nor can I tell which layer a node sits in as it depends on the links that are dynamically configured.

Beyond this a node can also be subsidiary to nodes in more than one level so it needs to sit at the lowest level - but I suspect if I can work out how to do the first bit i can do this too.