program Target;
{$APPTYPE CONSOLE}
{$HINTS OFF}

uses Windows;

var
  cs : RTL_CRITICAL_SECTION;

function ProtMB : LongWord; stdcall begin
  EnterCriticalSection(cs);
  Result := MessageBoxA(0,'Inside CS.','Target.exe', MB_OK);
  LeaveCriticalSection(cs);
end;

exports
  ProtMB;

begin
  InitializeCriticalSection(cs);
  //Block cs:
  //ProtMB;
  MessageBoxA(0,'Press OK to enter CS.','Target.exe',0);
  //Enter entered == blocked cs -> wait forever:
  ProtMB;
  DeleteCriticalSection(cs);
end.