L'ho trovata .... non è un API, ma semplicemnte l'overrides di WndProc

codice:
codice:Public Class Form1

    Const WM_NCHITTEST As Long = &H84
    Const HTCAPTION As Long = 2
    Const HTCLIENT As Long = 1


    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        MyBase.WndProc(m)
        Select Case m.Msg
            Case WM_NCHITTEST
                If m.Result.ToInt32 = HTCLIENT Then
                    m.Result = New IntPtr(HTCAPTION)
                End If
        End Select
    End Sub

    Private Sub btnChiudi_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnChiudi.Click
        Me.Close()
    End Sub
End Class
Facci sapere...
Ciao