Try the following function. WaitForSingleObject does what you need.
function ExecAppAndWait(const sApp, sParams: String; wShow: Word; sCurrentDirectory: String = ''): DWord;
{ Parameter wShow: SW_HIDE, SW_SHOWNORMAL, SW_NORMAL, SW_MAXIMIZE ...}
var
aSI : TStartupInfo; // Win32 : STARTUPINFO
aPI : TProcessInformation; // Win32 : PROCESS_INFORMATION
aProc : THandle; // Win32
aCurrentDirectory: PChar;
s: String;
begin
s := sApp + ' ' + sParams;
FillChar(aSI, SizeOf(aSI), 0);
aSI.cb := SizeOf(aSI);
aSI.wShowWindow := wShow;
aSi.dwFlags := STARTF_USESHOWWINDOW;
if sCurrentDirectory = '' then
aCurrentDirectory := nil
else
aCurrentDirectory := PChar(sCurrentDirectory);
Win32Check(CreateProcess(nil, PChar(s), nil, nil,
False, Normal_Priority_Class, nil, aCurrentDirectory, aSI, aPI));
// in TProcessInformation.hProcess -> Process-Handle
aProc := aPI.hProcess;
CloseHandle(aPI.hThread);
if WaitForSingleObject(aProc, Infinite) <> Wait_Failed then
GetExitCodeProcess(aProc, Result);
// free Ressource
CloseHandle(aProc);
end;