procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
if not (Key in ['0'..'9']) then
    Key := Chr(0); //禁止输入字符

end;

procedure TForm1.Button1Click(Sender: TObject);
begin
Edit1.SetFocus;                           //给于焦点
//SendMessage(Edit1.Handle,EM_SETSEL,0,1); //选择第一个字符
// SendMessage(Edit1.Handle,EM_SETSEL,0,-1); //全选
SendMessage(Edit1.Handle,EM_SETSEL,1,1); //光标移到第一个字符后面
//SendMessage(Edit1.Handle,EM_SETSEL,0,0); //光标移到开始
//SendMessage(Edit1.Handle,EM_SETSEL,-1,0); //光标移到开始

end;