Setting focus and nulling a field after a Length check

I have a form I'm working on which requires some basic length checks but I'm having trouble with one of my fields. In the change event I have this:

if (xfa,event.newText.match (/[^0-9/) !== null){

     this.rawValue = null;

     xfa.host.setFocus(this);

}

else if (xfa.event.newText.length > 9){

     this.rawValue = null;

     xfa.host.setFocus(this);

}

but it will not null the field or set the focus to the field when it fails either check. I'm not sure what the problem is though.

Thanks!