Public Class Form1
    Inherits System.Windows.Forms.Form
    Private _dev As Device
    Private _dev1 As Device
    Private _buffer As SecondaryBuffer
    Private _buffer2 As SecondaryBuffer

Private Sub Form4_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        _dev = New Device
        _dev.SetCooperativeLevel(Me.Handle, CooperativeLevel.Priority)
        _dev1 = New Device
        _dev1.SetCooperativeLevel(Me.Handle, CooperativeLevel.Priority)
    End Sub

    Private Sub btnSelFile_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSelFile.Click
        If ofd.ShowDialog Then
            _buffer = New SecondaryBuffer(ofd.FileName, _dev)
        End If
    End Sub
    Private Sub btnSelFile1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSelFile1.Click
        If ofd1.ShowDialog Then
            _buffer2 = New SecondaryBuffer(ofd1.FileName, _dev1)
        End If
    End Sub