Actually, no script is necessary and the answer is very easy.
You want to group the trigger with the helicopter. Perform the following steps:
1. Activate the Group feature (click on the Group button or press the F2 key).
2. Click on the trigger and hold the button.
3. Drag the mouse cursor over your helicopter and release the mouse button. A line should now be drawn from the trigger to the helicopter.
4. Open the Properties for the trigger by double-clicking on the trigger.
5. Change the Activated By options to Group or Vehicle, whichever you prefer.
6. Change the Present/Not Present parameter to Present.
That's it! Good luck!