主题：表的问题

试试

If e.DataCol.Name = "合同号" AndAlso e.DataRow("合同号") IsNot Nothing Then  '如果列名是合同号且合同号非空,即发现新增合同
    Dim cz As DataRow  '在应收帐表中查找与所选合同号一致的行
    cz= DataTables("表A").SQLFind("[单据号] = '" & e.DataRow("合同号") & "'")
    If cz Is Nothing '没找到就登帐
        e.DataRow.Save
        Dim nma() As String = {"合同号","负责人","客户"} '合同数据来源列
        Dim nmb() As String = {"单据号","负责人","客户"} '应收账表数据接收列
        Dim t As Double = DataTables("表B").SQLCompute("sum(数量*单价)","合同号='" & e.NewValue & " ' ")
        Dim dr As DataRow = DataTables("表A").AddNew
        For i As Integer = 0 To nma.Length - 1
            dr(nmb(i)) = e.DataRow(nma(i))
            dr("借方")= t
        Next
        dr.Save
    Else  '否则提出警告并返回
        MessageBox.Show("此合同已登帐!", "警告", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Return
    End If
End If

 最基础的，你还不会吗？修改数量、单价，肯定要重新计算的啊。

 例子 http://www.foxtable.com/help/topics/1472.htm