用System.type声明条件类型的对象

我正在尝试启动一个特定的表单,具体取决于双击事件上树视图的选定节点。启动窗体所需的代码有点庞大,因为在启动新实例之前,我必须确保窗体未被释放,并且窗体尚未打开。我希望所有这些检查都发生在函数末尾的一个地方,这意味着我必须能够将正确的表单类型传递给最后的代码。我试着用一个系统来做这个。键入,但似乎不起作用。有人能给我指一下正确的方向吗?

    With TreeView.SelectedNode
        Dim formType As Type
        Select Case .Text
            Case "Email to VPs"
                formType = EmailForm.GetType()
            Case "Revise Replacers"
                formType = DedicatedReplacerForm.GetType()
            Case "Start Email"
                formType = EmailForm.GetType()
        End Select
        Dim form As formType
         Dim form As formType
        Try
            form = CType(.Tag, formType)
            If Not form.IsDisposed Then
                form.Activate()
                Exit Sub
            End If
        Catch ex As NullReferenceException
            'This will error out the first time it is run as the form has not yet 
            ' been defined.
        End Try
        form = New formType
        form.MdiParent = Me
        .Tag = form
        CType(TreeView.SelectedNode.Tag, Form).Show()
    End With