Holty1-5

You have to use some kind of conditional script. Whether you complete a mission, obtain an item, or based upon a boolean statement; you need something to say if this has occurred then do that.

Here are two documents that I have that can help:

http://j.imagehost.org/download/0409/Conditional_Scripts

http://j.imagehost.org/download/0611/Boolean_and_Numbers_Tutorial