Grassy, Use Goal State Change in Mission Events. Create three Goal State Change events to change the User Flag controlling the C-130s. Three are required to cover the different possibilities of the order in which your ground targets are destroyed. I will call the three Goal State Events T1, T2, T3.
T1= Set GOAL as Must Destroy [your first ground object]. Then set a CONDITION of Must Destroy [your second ground object]= TRUE, AND set another CONDITION of Must Destroy [your third ground object]= TRUE. Set ACTION of User Flag controlling C-130s to TRUE.
T2= Set GOAL as Must Destroy [your second ground object]. Then set a CONDITION of Must Destroy [your first ground object]= TRUE, AND set another CONDITION of Must Destroy [your third ground object]= TRUE. Set ACTION of User Flag controlling C-130s to TRUE.
T3= Set GOAL as Must Destroy [your third ground object]. Then set a CONDITION of Must Destroy [your first ground object]= TRUE, AND set another CONDITION of Must Destroy [your second ground object]= TRUE. Set ACTION of User Flag controlling C-130s to TRUE.