Imports System.Runtime.InteropServices

Public Class Form1


    <DllImport("User32")> _
    Private Shared Function SetParent(ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As Integer
    End Function

    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindow( _
        ByVal lpClassName As String, _
        ByVal lpWindowName As String) As IntPtr
    End Function


    Private Const mconXLWindowClass As String = "XLMAIN"


    Private mXL As Object


    Private Sub btnBrowse_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnBrowse.Click

        Dim OFD As OpenFileDialog


        OFD = New OpenFileDialog()
        With OFD
            .CheckFileExists = True
            .CheckPathExists = True
            .Filter = "Test files (*.txt)|*.txt|Excel spreadsheets (*.xls, *.xlsx)|*.xls;*.xlsx|All files (*.*)|*.*"
            .FilterIndex = 2
            .InitialDirectory = System.Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
            .RestoreDirectory = True
            .Title = "Select Data File"
            If .ShowDialog = DialogResult.OK Then
                txtPath.Text = .FileName
                OpenExcel(tpDisplay.Handle, True)
                'OpenExcel(True)
            End If
        End With

    End Sub

    Private Sub OpenExcel(ByVal bShow As Boolean)

        OpenExcel(IntPtr.Zero, bShow)

    End Sub

    Private Sub OpenExcel(ByVal hwnd As IntPtr, ByVal bShow As Boolean)

        Dim hwndExcel As IntPtr


        Try


            mXL = CreateObject("Excel.Application")

            If hwnd <> IntPtr.Zero Then

                hwndExcel = FindWindow(mconXLWindowClass, mXL.Caption)
                SetParent(hwndExcel, hwnd)

            End If

            mXL.Visible = bShow
            OpenFile()


        Catch ex As Exception

            MsgBox(ex.Message)

        End Try

    End Sub


    Private Sub OpenFile()

        Dim objWorkbooks As Object


        objWorkbooks = mXL.Workbooks
        objWorkbooks.Open(txtPath.Text)

        While     (System.Runtime.InteropServices.Marshal.ReleaseComObject(objWorkbooks) > 0)
        End While
        objWorkbooks = Nothing

    End Sub

End Class