Concatination Fustulation

A random number between 1 and 10 is generated. There are 10 soundclips with the names cb1,cb2,cb3 etc

I want to concatinate(am I using that correctly?) the random number with cb to play one of those 10 sounds. The one thing I can tell you is that this code is not right!

var playCb:Number = Math.ceil(Math.random() * 10);

cbSoundChannel= cb[playCb].play();

I get an “undefined property cb” error cb1 would work as would cb2 etc.

Lil’ help