Панель элементов для создания формы

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
        Dim frm As New Form2
 
        frm.MdiParent = Me
        frm.Show()
 
    End Sub
 
End Class

Private Sub Form2_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown
        Me.Capture = False
        Me.WndProc(Message.Create(Me.Handle, &HA1, New IntPtr(2), IntPtr.Zero))
    End Sub

Public Class Form1
 
    Dim frm2 As New Form2
    Dim frm3 As New Form3
    
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim frm As New Form2
        frm.MdiParent = Me
        frm.Show()
    End Sub
 
    Private Sub Form1_Click(sender As Object, e As EventArgs) Handles Me.Click
 
    End Sub
 
    Private Sub TabControl1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles TabControl1.SelectedIndexChanged
        If TabControl1.SelectedIndex = 1 Then
            'Dim frm3 As New Form3 Если здесь(внутри) объявить переменную, а не глобально, то форма3 будет открываться повторно(множиться)
 
            frm3.MdiParent = Me
 
            Form2.Hide()
            frm3.Show()
 
 
        End If
    End Sub
End Class