[VB.NET] มีปัญหาอยากถามเกี่ยวกับ TREEVIEW ไม่สามารถเปิดฟอร์มครั้งที่สองได้

Private Sub TreeView1_AfterSelect(sender As Object, e As TreeViewEventArgs) Handles TreeView1.AfterSelect
        Select Case TreeView1.SelectedNode.Name
            Case Is = "matinv"
                If Application.OpenForms().OfType(Of matinv).Any Then
                Else
                    Dim status As New matinv
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "req"
                If Application.OpenForms().OfType(Of requisition).Any Then
                Else
                    Dim status As New requisition
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "viewStock"
                If Application.OpenForms().OfType(Of stockremain).Any Then
                Else
                    Dim status As New stockremain
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "transfer"
                If Application.OpenForms().OfType(Of tranfer).Any Then
                Else
                    Dim status As New tranfer
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "matdetail"
                If Application.OpenForms().OfType(Of matDetail).Any Then
                Else
                    Dim status As New matDetail
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "unit"
                If Application.OpenForms().OfType(Of unitDetail).Any Then
                Else
                    Dim status As New unitDetail
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "typedetail"
                If Application.OpenForms().OfType(Of typeDetail).Any Then
                Else
                    Dim status As New typeDetail
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "process"
                If Application.OpenForms().OfType(Of processDetail).Any Then
                Else
                    Dim status As New processDetail
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "pic"
                If Application.OpenForms().OfType(Of user).Any Then
                Else
                    Dim status As New user
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
            Case Is = "monthly"
                If Application.OpenForms().OfType(Of monthly).Any Then
                Else
                    Dim status As New monthly
                    status.MdiParent = Me
                    status.Show()
                    status.Location = New Point(0, 0)
                End If
        End Select
    End Sub