Actually you said "I DON'T want to copy and paste everything just so the loop is 3 times as long as it is originally..." so none of the solutions offered above involved copy and paste.
It now sounds like what you want is to place a loop within a project, and tell it to loop a certain number of times independently of any loop happening within the project itself. If I understand correctly, in your example there will be a 16 measure clip in the project that will play back and when the now time reaches the end of the clip, it will play back again, two more times, even though the now time will have moved past the clip.
If the person you're sending it to is using SONAR, this is not possible within track view. It is possible within Matrix view, although you would have to stop the loop playback manually while the rest of the song kept playing.