Unfortunatly RobotC does not have a random number function, at least as of version 1.46; I can't speak for the latest version though. If there were it would look something like this,
Note the comma, as written your code would set the lower bound at -200, not specify bounds of -100 and 100.
P.S. There is no "ght" in write and when used as a pronoun "I" is capitalized. FYI