add and remove TabControl com forms

Public Interface IFormsInTabs

    Function AddTab(ByVal frm As Windows.Forms.Form) As Integer 'to add new tab with form inside ;)
    Function RemoveTab() As Integer 'to close current tab

End Interface

Public Class TFormsInTabs
    Implements IFormsInTabs

    Private oTc As TabControl = Nothing 'we store a TabControl (from Form) in our class

    Public Sub New(ByVal _tc As TabControl)
        oTc = _tc '
    End Sub

    Public Function AddTab(ByVal frm As System.Windows.Forms.Form) As Integer Implements IFormsInTabs.AddTab
        Dim oTp As TabPage = Nothing 'a tabpage to add into TabControl

        Try
            oTp = New TabPage(frm.Text)
            frm.TopLevel = False
            oTp.Controls.Add(frm)
            frm.Dock = DockStyle.Fill
            frm.Show()
            oTc.TabPages.Add(oTp)
            oTc.SelectedTab = oTp

        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Error... {AddTab}")

        Finally
            oTp = Nothing
        End Try

    End Function

    Public Function RemoveTab() As Integer Implements IFormsInTabs.RemoveTab
        Try
            'removes current tab
            oTc.TabPages.Remove(oTc.SelectedTab)

        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Error... {RemoveTab}")
        End Try

    End Function

    Protected Overrides Sub Finalize()
        MyBase.Finalize()
    End Sub

End Class

Public Class MainFrm

    Dim mTC As IFormsInTabs = Nothing 'declare variable to store our class (using interface)

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        mTC = New TFormsInTabs(Me.TabControl1) 'here we call Public Sub New(Byval _tc As TabControl) in our class

    End Sub

    Private Sub TSMIOpenForm1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TSMIOpenForm1.Click
        Dim frm As Form1 = New Form1

        mTC.AddTab(frm)
        Me.TabControl1.Refresh()
    End Sub

    Private Sub TSMIOpenForm2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TSMIOpenForm2.Click
        Dim frm As Form2 = New Form2

        mTC.AddTab(frm)
        Me.TabControl1.Refresh()
    End Sub


    Private Sub CloseToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CloseToolStripMenuItem.Click
        mTC.RemoveTab()
        Me.TabControl1.Refresh()
    End Sub


    Protected Overrides Sub Finalize()
        MyBase.Finalize()
    End Sub

End Class