DELHI 7 калькулятор подскажите

как сделать чтобы калькулятор считал сразу несколько действий??? нажимая ровно только в конце.
unit Cal;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Edit1: TEdit;
Button1: TButton;
Button2: TButton;
Button3: TButton;
Button4: TButton;
Button5: TButton;
Button6: TButton;
Button7: TButton;
Button8: TButton;
Button9: TButton;
Button10: TButton;
Button11: TButton;
Button12: TButton;
Button13: TButton;
Button14: TButton;
Button15: TButton;
Button16: TButton;
procedure Button7Click(Sender: TObject);
procedure Button8Click(Sender: TObject);
procedure Button10Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure Button5Click(Sender: TObject);
procedure Button6Click(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button11Click(Sender: TObject);
procedure Button9Click(Sender: TObject);
procedure Button16Click(Sender: TObject);
procedure Button15Click(Sender: TObject);
procedure Button14Click(Sender: TObject);
procedure Button13Click(Sender: TObject);
procedure Button12Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
kod:char;
x,y,z:real;

implementation

{$R *.dfm}

procedure TForm1.Button7Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'1'
end;

procedure TForm1.Button8Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'2'
end;

procedure TForm1.Button10Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'3'
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'4'
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'5'
end;

procedure TForm1.Button6Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'6'
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'7'
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'8'
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'9'
end;

procedure TForm1.Button11Click(Sender: TObject);
begin
edit1.Text:=edit1.Text+'0'
end;

procedure TForm1.Button9Click(Sender: TObject);
begin
edit1.clear;
end;

procedure TForm1.Button16Click(Sender: TObject);
begin
if edit1.Text<>'' then x:=strtofloat(edit1.Text);
kod:='+';
edit1.clear;
end;

procedure TForm1.Button15Click(Sender: TObject);
begin
if edit1.Text<>'' then x:=strtofloat(edit1.Text);
kod:='-';
edit1.clear;
end;

procedure TForm1.Button14Click(Sender: TObject);
begin
if edit1.Text<>'' then x:=strtofloat(edit1.Text);
kod:='*';
edit1.clear;
end;

procedure TForm1.Button13Click(Sender: TObject);
begin
if edit1.Text<>'' then x:=strtofloat(edit1.Text);
kod:='/';
edit1.clear;
end;

procedure TForm1.Button12Click(Sender: TObject);
begin
if edit1.text<>'' then y:=strtofloat(edit1.Text);
case kod of
'+':z:=x+y;
'-':z:=x-y;
'*':z:=x*y;
'/':z:=x/y;
end;
edit1.Text:=floattostr(z);
end;
end.

да