procedure TForm1.FormCreate(Sender: TObject);
begin
ProgressBar1.Parent := Button1;
ProgressBar1.Width := Button1.Width-7;
ProgressBar1.Height := Button1.Height-7;
ProgressBar1.Left := 3;
ProgressBar1.Top := 3;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
i : byte;
begin
Button1.Enabled := false;
if ProgressBar1.Visible then Exit;
ProgressBar1.Position := 0;
ProgressBar1.Visible := True;
for i := 0 to 99 do
begin
Sleep(100);
ProgressBar1.Position := ProgressBar1.Position + 1;
Application.ProcessMessages;
end;
ProgressBar1.Visible := False;
Button1.Enabled := true;
end;