C#操作Excel新添加右键菜单项的问题（Winform）

各位好！
在做用代码控制Excel的功能。比如控制打开Excel之后，用代码将Excel右键菜单新增一项“aa”,并对其定义新的方法。
看代码：
-------------------
#endregion
#region Excel support code
public ContextMenu m_RMBContextMenu = null;
Excel.Application exApp = null;
Microsoft.Office.Core.CommandBarButton cbb = null;
Microsoft.Office.Core.CommandBar t = null;
public void NewWorkbook(Excel.Workbook Wb)
{
System.Diagnostics.Debug.WriteLine("NewWorkbook");
exApp = Wb.Application;
object type = 1;
object oMissing = System.Reflection.Missing.Value;
//find the cell menu and then disable all and then add the ones we want
int cnt =
(int)exApp.CommandBars.GetType().InvokeMember("Count", System.Reflection.BindingFlags.GetProperty, null, exApp.CommandBars, new object[] { });
for (int i = 1; i <= cnt; i++)
{
t =
(Microsoft.Office.Core.CommandBar)exApp.GetType().InvokeMember("CommandBars", System.Reflection.BindingFlags.GetProperty, null, exApp, new object[] { i });
if (t.Name == "Cell")
{
t.Reset();
for (int j = 1; j <= t.Controls.Count; j++)
t.Controls[j].Visible = false;
cbb =
(Microsoft.Office.Core.CommandBarButton)t.Controls.Add(type, oMissing, oMissing, oMissing, oMissing);
break;
}
}
cbb.Caption = "Hello";
cbb.Click += new
Microsoft.Office.Core._CommandBarButtonEvents_ClickEventHandler(cbb_Click);
}

private void cbb_Click(Microsoft.Office.Core.CommandBarButton Ctrl, ref bool CancelDefault)
{
Console.WriteLine("cbb_Click");
}

public void WorkbookBeforeClose(Excel.Workbook Wb, ref bool Cancel)
{
t.Reset(); //reset the menu
System.Diagnostics.Debug.WriteLine("WorkbookBeforeClose");
}

#endregion
-------------------
但近来遇到一个奇怪棘手的问题，受阻！！！ 如下：
(Microsoft.Office.Core.CommandBarButton)t.Controls.Add(type, oMissing, oMissing, oMissing, oMissing);

//每次执行到这一句，代码就跳出了，也不提示出错，VBA中这句也没错，VSTO中也没错，就是在C#Winform中,执行完这句就跳出了。 而且浮动工具栏的新增不存在这个问题，仅仅针对右键菜单就出现这个问题！

高手指教！（代码来自微软官方技术支持）