"Add Item" Button with multiple dropdown values

[the1h3r0]

Okay so I'm trying to write a script that generates the MySQL code for a DayZ inventory using simple dropdowns.  The code format for the mysql code is:

[["primaryweapon","secondaryweapon"],["item1","item2",...etc]]

I know how I'm going to use dropdown lists to fill in the primary and secondary weapons, but not so much for the items.  All the items in DayZ will be in this one dropdown list and I want it to be so when you select which item you want and click an "Add Item" button it will echo a live output of the code so far.  I'm not sure how to make it so the next item in the code is filled in properly all using one dropdown list.  Is there any way of accomplishing this?  Sorry if it's a bad explination as to what I need, I just really don't know how to describe it.  Essentially I want it to look like this: