your excel file path   
Dim path As String = Server.MapPath("~/Uploads/" & fileUpload.FileName)
Dim objexcel As New Excel.Application
        Dim o_nullobject As Object = System.Reflection.Missing.Value
        Dim o_filePath As Object = path
        Dim doc As Excel.Workbook = objexcel.Workbooks.Open(o_filePath, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject)
        Dim o_newfilename As Object = Server.MapPath("~/Uploads/") & _
                    fileUpload.FileName.Replace(".xls", ".html")
        Dim o_format As Object = Excel.XlFileFormat.xlHtml
        Dim o_encoding As Object = Microsoft.Office.Core.MsoEncoding.msoEncodingUTF8
        'Dim o_endings As Object = Excel.xll.WdLineEndingType.wdCRLF
        objexcel.ActiveWorkbook.SaveAs(o_newfilename, o_format, o_nullobject, o_nullobject, o_nullobject, o_nullobject, Excel.XlSaveAsAccessMode.xlNoChange, o_nullobject, o_nullobject, o_nullobject, o_nullobject, o_nullobject)
        lblMessage.Text = "Uploaded successfully!"
        doc.Close(o_nullobject, o_nullobject, o_nullobject)