Add a Priority instance variable to the family, say, from 1 (lowest) to 5 (highest). Then you can use the Pick lowest condition:
For each Enemy
Enemy has LineOfSight to Object
Object pick instance with lowest (distance(Object.x, Object.y, Enemy.X, Enemy.Y)/Object.Priority)
... Enemy Move to Object
Say, object A has priority 2 and is 100px away, object B has priority 5 and is 300px away. Object A will be picked.
You can tweak the formula if needed.