我要设计一个案卷目录

序号           内    容                  页数         合计页            起始页号       终止页号        顺序号

1              受案表                      2              2                     1                 2             1－2

2              现场图                      1              3                     3                 3                3 

3              现场勘查笔录              4              7                     4                 7             4－7

现请问，怎样实现填入页数，自动计算出合计页的数据。如现场图一行如何按受案表页数2与现场图页数1相加得出3，即同一表中下一行如何引用上一行的数据。请老师们指点。

Dim t As Table = Tables("案卷目录")
t.Sort = "_SortKey"
For i As Integer = 0 To t.Rows.Count - 1
    Dim sum As Integer = 0
    For j As Integer = 0 To i

        sum + = t.Rows(j)("页数")
    Next
    t.Rows(i)("合计页") = sum
Next