Como pegar a url ativa no browser?

Uses ddeman;

function GetURL(Service: string): String;
var
ClDDE: TDDEClientConv;
temp:PChar;
begin
Result := '';
//create a new DDE Client object
ClDDE:= TDDEClientConv.Create( nil );
with ClDDE do
begin
SetLink(Service,'WWW_GetWindowInfo');
temp := RequestData('0xFFFFFFFF');
Result := StrPas(temp);
StrDispose(temp);
CloseLink;
end;
ClDDE.Free;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(GetURL('IExplore'));
end;