主题：配置栏动态标签

想在菜单的配置栏动态显示用户名和时间,以下代码为何不行?

Dim Str1 As String = "当前用户: " & User.Name
Dim Str2 = Str1 & "   当前时间: " & Format (now, "D") & Format(now, "dddd ") & ""
RibbonMenu.ConfigBar.Items("标签1").text = Str2