为什么WebBrowser中Document的onclick事件引发很多问题？

VB.NET code

Public Class Form1    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load        Me.WebBrowser1.Navigate("http://www.baidu.com")    End Sub    Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted        Dim doc As mshtml.HTMLDocument = Me.WebBrowser1.Document.DomDocument        Dim docevents As mshtml.HTMLDocumentEvents2_Event = DirectCast(doc, mshtml.HTMLDocumentEvents2_Event)        AddHandler docevents.onclick, AddressOf Me.Doc_onclick    End Sub    Private Function Doc_onclick(ByVal obj As mshtml.IHTMLEventObj) As Boolean        Debug.Print(obj.x)        obj.returnValue = True        Return True    End FunctionEnd Class

我在VB里成功拦截了document的onclick事件后，出现了所有鼠标事件（如右键、选择）失效的问题，不知什么原因？莫非是因为document的onclick事件为非托管造成的？

[解决办法]
不懂，是不是还需要CallWindowProc（）
[解决办法]
答案是什么
是obj.returnValue = True造成的