How to Search a File through all the SubDirectories in Delphi

I have implemented this code in Delphi, it will search for the File or the name given but it omits searching all the subdirectories. How can this be done?

Code:

 if FindFirst(filePath,faAnyFile,searchResult)=0 then
  try
    repeat
    lbSearchResult.Items.Append(searchResult.Name);

    until FindNext(searchResult)<>0
  except
  on e:Exception do
  ShowMessage(e.Message);
  end; //try ends
  FindClose(searchResult);