[n[ate]vw]

Because your program must loop repeatedly, you will have to store, in a variable or in the extra RAM, a number that will tell you what state your program should be in.
For example, the first time it detects the button, it would start moving the arm, and store a value so that the next time your program goes through the loop, it will do the next operation (or wait a few loops first). I think the RC is designed to loop about 25 times/sec. You can't pause during a loop to wait for your arm to close or something, or you will start dropping packets and wind up with an error, most likely.

Hope this helps.