FMB Quest - Setting Up Targets

[Racetrack]

Hi guys! I've some problems here..
I'm making some historical mission and I don't know clearly how to deploy Primary and Secondary Target.
It is possible to set a "Destroy Bridge" for the Reds (with timer) and at the same time set a "Defend Bridge" for the Blues?
What I want is to force the Reds to attack the bridge before the timer countdown will elapsed to win the game..
If instead they don't do that the Blues will win.
Another question, I want that the Blues will attack (in another mission) a convoy destroying at least 75% of the ships forming the convoy
before the countdown will elapsed to win the game.. If instead they don't do that the Reds will win.
Do I have to set one "Destroy Ground" in the zone where all the ships spawn ? With an ammount of 75% and a one Timer?
Or I have to set up one "Destroy" for every ship?