Retrouver la dernière occurence dans un string

function LastPos(SubStr, S: string): Integer;
var
Found, Len, Pos: integer;
begin
Pos := Length(S);
Len := Length(SubStr);
Found := 0;
while (Pos > 0) and (Found = 0) do
begin
if Copy(S, Pos, Len) = SubStr then
Found := Pos;
Dec(Pos);
end;
LastPos := Found;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
showmessage('Dernier occurence de le se trouve en '+
inttostr(LastPos('le', 'le le le la le')));
end;