ขอสอบถามเรื่องสูตร Excel หน่อยครับ

Option Explicit
Sub Shelf_Allocate()
Dim i, j, k As Integer
Dim over As Integer
Dim distribute As String
Dim product As String
Dim amount As Integer
Dim accum As Integer
Dim ShelfCode As String
Dim ShelfCapacity As Integer
j = 4
For i = 4 To 28
    If j > 12 Then
        amount = 0
    End If
        ShelfCode = Cells(i, 1).Value
        ShelfCapacity = Cells(i, 2).Value
        product = Cells(j, 4).Value
        amount = Cells(j, 5).Value
        If accum > 0 Then
             amount = amount - accum
        Else
            amount = Cells(j, 5).Value
        End If
     If ShelfCapacity < amount Then
            accum = accum + ShelfCapacity
             amount = ShelfCapacity
             over = amount - ShelfCapacity
             distribute = ShelfCode & " | " & ShelfCapacity & " >> " & product & " | " & amount
        Else
        accum = 0
            distribute = ShelfCode & " | " & ShelfCapacity & " >> " & product & " | " & amount
            j = j + 1
     End If
Range("G" & i).Value = ShelfCode
Range("H" & i).Value = ShelfCapacity
Range("I" & i).Value = product
Range("J" & i).Value = amount
'Debug.Print (distribute)
Next i
End Sub