In our church every time someone comes into the building through the main entrance, the interior main sanctuary doors come open and make it possible to hear noise from the hallway. Is there some piece of hardware that can be installed on the sanctuary doors to prevent them from opening from the exchange of air flow but still allow entrance into the sanctuary?
You have two problems really and you can choose to solve one, the other or both.
First is the easier one, securing your doors so they can't be opened by the air. As Gunner mentioned, a ball latch/catch might work however they are designed to allow the door to open with a bit of force.
Other options include a bolt that you manually open at the top/bottom, or a panic bar:
The second way to tackle this problem is to prevent the vacuum that is occurring when the doors are opened. You likely need vents to allow air to flow between the two rooms - either slats in the door or more dedicated HVAC.