foreach (Microsoft.Office.Interop.Word.Range tmpRange in oDoc.StoryRanges)
{
  tmpRange.Find.Text = "{Date}";
  tmpRange.Find.Replacement.Text = DateTime.Now.ToString("MM/dd/yyyy");
  tmpRange.Find.Wrap = Microsoft.Office.Interop.Word.WdFindWrap.wdFindContinue;
  object replaceAll = Microsoft.Office.Interop.Word.WdReplace.wdReplaceAll;
  tmpRange.Find.Execute(ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing,
                        ref missing, ref missing, ref missing, ref replaceAll,
                        ref missing, ref missing, ref missing, ref missing);
}