form如何共享，等待？

写个群注的程序，一个form页负责验证码的输入，
  if suiCheckBox1.Checked then
  begin
    Sinaform();
  end;
  if suiCheckBox2.Checked then
  begin
    wyform();
  end;
这样写第一个验证码还没输入就进行到第二个了，怎样等待sinaform完成后再进行wyform，procedure sinaform();
var
  code: string;
  imagestream: TMemoryStream;
  png: TPNGObject;
begin
  sinahttp:= Tidhttp.create;
  sinahttp.Request.UserAgent:= 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.8 (KHTML, like Gecko) Chrome/4.0.288.1 Safari/532.8';
  sinahttp.Request.Accept:= 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5';
  sinahttp.Request.AcceptLanguage:= 'zh-CN,zh;q=0.8';
  sinahttp.Request.Referer:= 'http://login.sina.com.cn/signup/signup.php';
  imagestream:= TMemoryStream.Create;
  png := TPngObject.Create;
  Randomize;
  code:= Inttostr(Random(99999999));
  try
    sinahttp.Get('http://login.sina.com.cn/cgi/pin.php?r='+ code,imagestream);
    Sleep(500);
    try
      imagestream.Position:=0 ;
      png.LoadFromStream(imagestream);
      form2.Image1.picture.assign(png);
    finally
      png.Free;
      imagestream.Free;
    end;
    form2.Show;
  finally
  end;
end;