Public Class Form1
    Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" ( _
      ByVal hwnd As IntPtr, ByVal wMsg As Int32, ByVal wParam As Int32, ByVal _
      lParam As IntPtr) As Int32
    Private Declare Function ReleaseCapture Lib "user32.dll" () As Int32
    Const HTCAPTION As Int32 = &H2
    Const WM_NCLBUTTONDOWN As Int32 = &HA1
 
    Private Sub Panel1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseDown
        ReleaseCapture()
        SendMessage(Me.Handle, WM_NCLBUTTONDOWN, HTCAPTION, IntPtr.Zero)
    End Sub
End Class