ActionScript 2.0 Language Reference - Adobe Help and Support

You must define a function that executes when the event handler is invoked. You can define
the function on the timeline or in a class file that extends the MovieClip class or is linked to a
symbol in the library.
Availability: ActionScript 1.0; Flash Player 6
Example
The following example defines a function for the onRollOver() method that sends a
trace() action to the Output panel:
my_mc.onRollOver = function () {
trace("onRollOver called");
}
onSetFocus (MovieClip.onSetFocus handler)
onSetFocus = function(oldFocus:Object) {}
Invoked when a movie clip receives keyboard focus. The oldFocus parameter is the object
that loses the focus. For example, if the user presses the Tab key to move the input focus from
a movie clip to a text field, oldFocus contains the movie clip instance.
If there is no previously focused object, oldFocus contains a null value.
You must define a function that executes when the event handler in invoked. You can define
the function on the timeline or in a class file that extends the MovieClip class or is linked to a
symbol in the library.
Availability: ActionScript 1.0; Flash Player 6
Parameters
oldFocus:Object - The object to lose focus.
Example
The following example displays information about the movie clip that receives keyboard
focus, and the instance that previously had focus. Two movie clips, called my_mc and
other_mc are on the Stage. Add the following ActionScript to your AS or FLA document:
my_mc.onRelease = Void;
other_mc.onRelease = Void;
my_mc.onSetFocus = function(oldFocus) {
trace("onSetFocus called, previous focus was: "+oldFocus);
}
Tab between the two instances, and information displays in the Output panel.
922 ActionScript classes