主题：在下面代码中如何使库存的累计也为36，而不是累计为222呢?

Dim t As Table = Tables("例子二")
Dim g As Subtotalgroup
t.SubtotalGroups.Clear()
t.GroupAboveData = False
t.TreeVisible = False
t.SpillNode = True

g = New Subtotalgroup
g.Aggregate = AggregateEnum.Sum
g.GroupOn = "日期"
g.TotalOn = "入库,出库,库存"
g.Caption = "{0}月 小计"
g.DateGroup = DateGroupEnum.Month
t.SubtotalGroups.Add(g)

g = New Subtotalgroup
g.Aggregate = AggregateEnum.Sum
g.GroupOn = "日期"
g.TotalOn = "入库,出库,库存"
g.Caption = "{0}月 累计"
g.DateGroup = DateGroupEnum.Month
t.SubtotalGroups.Add(g)
t.Subtotal

For i As Integer = 0 To CurrentTable.Rows.Count(True) - 1
    Dim r As Row = CurrentTable.Rows(i,True)
    If r.IsGroup
        r("库存") = r("入库")- r("出库")
    End If
Next

If e.DataCol.Name = "第一列" Then
    Dim dr As DataRow
    dr = e.DataTable.Find("第一列 = '" & e.NewValue & "'")
    If dr IsNot Nothing Then
        MessageBox.Show("此第一列已经存在!")
        e.Cancel = True
    End If
End If

怎么我用了还是能输入重复值吗？那里有错

做个例子传上来看看。