Linking box sprites (extra field)

local function tileWithBox(i,j)

    local tile = gameTile(i,j)
    tile.isBox = true
    tile.isWalkable = false

    local tileWithBox

    trackID = trackID + 1
    tile.box = display.newImage("crate.png")
    tile.box.i = i
    tile.box.j = j
    tile.box.x = 240-((8 * 17) +17) +(i*34)
    tile.box.y =  (j * 34)
    tile.box.myID = trackID

    return tile
end