刚开始的写法是：
function limitToNum(){
if (this.text != "-" && isNaN(this.text)) {
this.text = ’’;
}
}
a_txt.onChanged = limitToNum;
b_txt.onChanged = limitToNum;
c_txt.onChanged = limitToNum;
...发现有点繁琐，突然想起'prototype'：
TextField.prototype.onChanged = function() {
if (this.text != "-" && isNaN(this.text)) {
this.text = ’’;
}
};这样就限制了Flash中所有的动态文本输入框。
由此还可以类推。比如：
MovieClip.prototype.onPress = startDrag;
MovieClip.prototype.onRelease = stopDrag;
MovieClip.prototype.onReleaseOutside = stopDrag;这样Flash中所有的剪片剪辑都可以被拖拽了。
:) enjoy!