Dim trv As WinForm.TreeView = e.Form.Controls("TreeView1")
Dim nd As WinForm.TreeNode = trv.SelectedNode
If nd IsNot Nothing Then
    If nd.Level = 2 Then
        MessageBox.Show("最多允许三层节点!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
        \'ElseIf nd.Level = 0
        \'    MessageBox.Show("不能选择工程名称!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    ElseIf nd.Level > 0 Then

        Dim pr As DataRow = DataTables("项目结构").find("_Identify = " & nd.tag)
        \'Dim pr As DataRow = e.node.DataRow
        Dim dr As Row = Tables("项目结构").AddNew()
        dr("项目编号") = pr("项目编号")
        dr("工程名称") = pr("工程名称")
        \'dr("标段名称") = pr("标段名称")
        dr("单位工程") = "单位工程"
        Dim bh As String = DataTables("项目结构").Compute("max(专业编号)","项目编号 = \'" & pr("项目编号") & "\'")
        Dim id As Integer = 0
        If bh > "" Then
            id = cint(bh.SubString(pr("项目编号").Length + 1,2)) + 1
        End If
        dr("专业编号") = pr("项目编号") & "-" & Format(id,"00")
        If nd.Level = 1
            nd = nd.Nodes.Add("单位工程")
        ElseIf nd.Level = 2
            nd = nd.ParentNode.Nodes.Add("单位工程")
        Else
            nd = nd.ParentNode.ParentNode.Nodes.Add("单位工程")
        End If
        nd.tag = dr("_Identify")
        trv.SelectedNode = nd
        trv.Select()
        trv.BeginEdit()
    End If
End If

回复11楼，参考

http://www.foxtable.com/webhelp/scr/3116.htm