Delphi executes an external program, and when the external program finishes, the Delphi program responds immediately

Need to refer to SHELLAPI unit;
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);      Paramstring can contain the application parameters//Lpparameters: = PChar (paramstring);  startinstring Specifies the name of the working Directory.if ommited, the current directory is used.      Lpdirectory: = PChar (startinstring);    Nshow: = Sw_shownormal;    End        If ShellExecuteEx (@SEInfo) then BEGIN repeat application.processmessages;        GetExitCodeProcess (seinfo.hprocess, ExitCode);      If ExitCode = Still_active then Sleep (500);      Until (ExitCode <> still_active) or application.terminated; ShowmesSage (' Calculator terminated ');  End Else ShowMessage (' Error starting calc! ');   End

Delphi executes an external program, and when the external program finishes, the Delphi program responds immediately