This invention provides a mechanism for enhancing safe use of wireless mobile terminals (smartphones) in a moving vehicle. The Invoke facility service's Boolean expression controls the conditions which invoke smartphone apps into execution. Smartphone apps, which are dangerous to execute in a moving vehicle, are prevented from invocation. Elimination of all smartphone apps in moving vehicles is inadvisable. An app, deploying an accelerometer to sense the impact of a serious collision to call “911” with a recorded message and provides the vehicle's GPS location, is an example. This invention allows an app builder to select invocation conditions for apps. Significant is the use manner of the operation “Not”. The contradiction of an event is also an event meaning that if an event is false, its contradictory event is true. Another important aspect is the conjunctive operation “And Then”. This operation implies an efficient algorithm to evaluate Boolean expressions.