I think in your existing code please make this type of modification...
string filePath = Application.StartupPath + "\\Preseaintake\\newtest.xls";
if(System.IO.File.Exists(filePath))
System.IO.File.Delete(filePath)
xlWorkBook.SaveAs(filePath, misvalue, misvalue, misvalue, misvalue, misvalue, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, misvalue, misvalue,
misvalue, misvalue, misvalue);
xlWorkBook.Close(true, misvalue, misvalue);
xlsheet = null;
xlapp = null;