在VB中，可以使用API函数FindWindow和FindWindowEx来查找无句柄窗口。以下是一个示例代码，演示如何使用这些函数来获取Windows资源管理器的树视图控件的句柄：

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWndParent As Long, ByVal hWndChildAfter As Long, ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Private Sub CommandButton1_Click()

    Dim hTreeview As Long

    Dim hDesktop As Long

    ' 获取桌面窗口句柄

    hDesktop = FindWindow("Progman", vbNullString)

    hDesktop = FindWindowEx(hDesktop, 0&, "SHELLDLL_DefView", vbNullString)

    hDesktop = FindWindowEx(hDesktop, 0&, "SysListView32", "FolderView")

    ' 获取树视图控件句柄

    hTreeview = FindWindowEx(hDesktop, 0&, "SysTreeView32", vbNullString)

    ' 检查是否成功获取了树视图控件句柄

    If hTreeview <> 0 Then

        MsgBox "树视图控件句柄为：" & hTreeview, vbInformation, "无句柄窗口获取"

    Else

        MsgBox "未能获取树视图控件句柄", vbCritical, "无句柄窗口获取"

    End If

End Sub

以上代码将在单击按钮时查找Windows资源管理器的树视图控件，并显示其句柄。请注意，此示例只适用于Windows 7和较早版本的操作系统。在Windows 8及更高版本中，Windows资源管理器的架构发生了变化，因此该方法可能不起作用。