Delphi 执行一个外部程序，当外部程序结束后言主程序立即响应

uses shellAPI;

procedure TForm1.Button1Click(Sender: TObject);
var
SEInfo: TShellExecuteInfo;
ExitCode: DWORD;
ExecuteFile, ParamString, StartInString: string;
begin
ExecuteFile := ‘c:/Windows/system32/Calc.exe‘;
FillChar(SEInfo, SizeOf(SEInfo), #0);
SEInfo.cbSize := SizeOf(TShellExecuteInfo);
with SEInfo do begin
fMask := SEE_MASK_NOCLOSEPROCESS;
Wnd := Application.Handle;
lpFile := PChar(ExecuteFile); nShow := SW_SHOWNORMAL;
end;
if ShellExecuteEx(@SEInfo) then
begin
repeat
Application.ProcessMessages;
GetExitCodeProcess(SEInfo.hProcess, ExitCode);
if ExitCode = STILL_ACTIVE then Sleep(50);
until (ExitCode <> STILL_ACTIVE) or Application.Terminated;
ShowMessage(‘Calculator terminated‘);
end
else
ShowMessage(‘Error starting Calc!‘);
end;