[New]C++ Code

// How long should we allow for the 3 presses?
double timeSpan = 5.0;  // let's go with 5 seconds for this example as you asked

int counter = 0;  // used to count number of times Enter is pressed

// VARIABLES FOR TIMING
LARGE_INTEGER frequency;
LARGE_INTEGER startTime, currentTime;
double elapsedTime = 0;
QueryPerformanceFrequency(&frequency);
QueryPerformanceCounter(&startTime);


// CHECK for KEY PRESS
if(GetAsyncKeyState(VK_RETURN))
{
  // Calculate the time from last press
  QueryPerformanceCounter(&currentTime);
  elapsedTime = (currentTime.QuadPart - startTime.QuadPart) * 1000.0 / frequency.QuadPart;

  // If we are within the set time
  if(elapsedTime < timeSpan)
  {
     counter++;
  }
  else
  {
    // Set a new start time
    QueryPerformanceCounter(&startTime);
    counter = 1;
  }

  //Are we at 3 or more clicks of enter?
  if(counter >= 3)
  {
     exit(-1);  // exit the game
  }
}

Compiling...
Entercount.cpp
C:\Users\Administrator\Desktop\Enter\Entercount.cpp(197) : error C2065: 'VK_ENTER' : undeclared identifier
C:\Users\Administrator\Desktop\Enter\Entercount.cpp(211) : error C2065: '$startTime' : undeclared identifier
Error executing cl.exe.

Entercount.dll - 2 error(s), 0 warning(s)