procedure TForm1.sButton1Click(Sender: TObject);
var
i : integer;
begin
for i := 1 to 4 do
if FindComponent('sLabelFX' + IntToStr(i)) is TsLabelFX then
with FindComponent('sLabelFX' + IntToStr(i)) as TsLabelFX do
Caption := 'My Label ' + IntToStr(i);