"number of objective" objstatus "DONE"
the number is what objective it is (i.e. 1st thing you gotta do is blow something up, when you done that, 1st obj. will be checked. if 2nd thing is, repair it again, you must put "2"objstatus "DONE" to let that one be checked)
at DONE, you can also put FAIL (or FAILED, not sure) and HIDDEN. to activate HIDDEN you must prolly use ACTIVE, but I'm not sure about that either
sry, but you can easily look this up in the tutorials
***EDIT***
Ace is right, most topics like these are covered by tutorials. Read the thread at the top of the forum also.