主题：如何增加并算出当前余额？

自定义汇总模式代码：

Dim t As Table = Tables("消费明细2011年")
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 = "消费日期"
g.TotalOn = "消费金额"
g.Caption = "{0}月 小计"
g.DateGroup = DateGroupEnum.Month
t.SubtotalGroups.Add(g)

g = New SubtotalGroup
g.Aggregate = AggregateEnum.Sum
g.GroupOn = "*"
g.TotalOn = "消费金额"
g.Caption = "总计"
g.upto = True
t.SubtotalGroups.Add(g)

g = New Subtotalgroup
g.Aggregate = AggregateEnum.Sum
g.GroupOn = "*"
g.TotalOn = "消费金额"
g.Caption = "总计"
t.SubtotalGroups.Add(g)

t.Subtotal()

Dim sum1 As Decimal = DataTables("收入明细2011年").Compute("Sum(收入金额)")
Dim sum2 As Decimal = DataTables("消费明细2011年").Compute("Sum(消费金额)")
Dim r As Row
For i As Integer = 0 To Tables("消费明细2011年").Rows.Count(True) - 1
    r = CurrentTable.Rows(i,True)
    If r.IsGroup
        If i = Tables("消费明细2011年").Rows.Count(True) -1 Then
            r("消费日期") = "当前余额"
            r("消费金额") = sum1-sum2
        End If
    End If
Next