One button, two MC's controlled

I have one MC with the following AS:
[INDENT]stop();
this.onEnterFrame = function() {
if (rewind == true) {
prevFrame();
}
}
_root.about_btn.onRollOver = function() {
rewind = false;
play();
}
_root.about_btn.onRollOut = function() {
rewind = true;
}[/INDENT]

This works fine. However, I want the button “about_btn” to also control a second MC, but flip the rewind properties, like so:
[INDENT]stop();
this.onEnterFrame = function() {
if (rewind == true) {
prevFrame();
}
}
_root.about_btn.onRollOver = function() {
rewind = true;
}
_root.about_btn.onRollOut = function() {
rewind = false;
play();
}[/INDENT]

but no such luck with the second MC. Even if I apply the same AS code to the second MC, it still won’t work. Thoughts?