I noticed your frustration of trying to get a inventory system working in AS2
I highly recommend you move to as3 but for now I will tell you how a inventory system works in as2. Before you start coding you need to know how the code gets executed and what happens first, how fast it gets executed.
I will tell you the easiest way to do this, You can start by making a Movie Clip. This Movie clip will be your inventory slot
The first frame of the movieclip will be a empty slot, The second frame will be a slot with a item in example (HP potion), The third frame will be a slot with another item in, For example a mana potion.
You then need to make an array, With empty strings in for how many inventory slots you got
var invarray:Array = new Array("Empty", "Empty", "Empty");
Lets say we have 3 inventory slots
An Array will hold multiple values, In this case we are going to pass our items as strings.
Then after the array is made you need to make a function which will add items to the array
So lets start
var addonce:Boolean = false;
if(invarray[a] == "Empty")
invarray[a] = item;
addonce = true;
The add once variable stops the for statement finding all slots that are empty and just finds the first one
After this we need to display the items in the inventory
As you can see we call this function from the AddItemsToMyArray function
if(invarray[i] == "ManaPotion")
if(invarray[i] == "HPPotion")
As you can see we have declared something called invSlotsArray, This will hold your inventory slots.
Now go back to the top and make it
var invSlotsArray:Array = new Array(_root.invs1, _root.invs2, _root.invs2)
This will hold your inventory slots, Now go back to your scene and copy the inventory slot we made earlier, Now there are 3, Give them a instance name of invs1, invs2 and invs3.
If anything was wrong or you don't understand, I made these tutorials a few years back