Men Of War: Red Tide mission question

[imran764]

Company of Heroes:
2nd Mission: The fall of the stronghold Nikolaev
Objective: Take up a suitable position in the building to adjust artilery fire and destroy the enemy command post.

well i have a problem with this mission. i have killed every enemy unit and destroyed their vehicles. but when i go to the building nothing happens. even i have destroyed the building but still nothing

how could i clear that mission. help please