You have to create a loop that updates the camsettarget every ~0.01 second or so.
I'm at work, so I cannot give you the syntax, but here is what you do...
unPbo the Red Hammer campaign and look in the first mission. ThereĆ's a camera following a flying helo in that one. The camera script is in init.sqs.
They use a counter that determines when the loop is finished, and then they update the script continuosly. have a look at it, it's pretty simple and this is where I learned to make loop scripts.