TabNavigator.selectedIndex problem

Question

What I'm trying to do, is some data validation before allowing a user to change tabs, so I put some code in the change handler on the tabNavigator, which fires when a user clicks another tab. If the validation fails, then the code sets the selectedIndex back to the index of the previous tab.
This all works fine, but for some reason, the tab which was clicked on becomes a "dead" tab, and no longer fires a change event when clicked on. Anyone know what is happening here, or a way to correct this issue?
I've tried tabNavigator.validateNow(), but that didn't seem to do much.
Many thanks!

Answer 1

Thanks for your input David. Basically, the client wants the app to check to make sure a user has entered certain data before allowing them to leave the current tab. The action the user takes, will be clicking on another tab, so the change event seems like the only place I can capture this action and alert the user they need to do something.
Here is an example of what the code looks like:
<?xml version="1.0" encoding="utf-8"?>
<mx:Application  xmlns:mx="http://www.adobe.com/2006/mxml">
     <mx:Script>
          <![CDATA[
          import  mx.events.FlexEvent;
          import  mx.events.IndexChangedEvent;
          protected function handleTnChange(e:Event):void
               var failed:Boolean = true;
               //Assume validation failed for test
               if (failed) {
                    tn.selectedIndex = _tnSelectedIndex; //tnSelectedIndex holds the previous selected tab index before the user click
               else{
                    //Proceed to the selected tab
     ]]>
     </mx:Script>
     <mx:TabNavigator  id="tn" change="handleTnChange(event)">
          <mx:Canvas label="Tab 1"  width="100%" height="100%">
          </mx:Canvas>
          <mx:Canvas label="Tab 2" width="100%" height="100%">
          </mx:Canvas>
          <mx:Canvas label="Tab 3" width="100%" height="100%">
          </mx:Canvas>
     </mx:TabNavigator>
</mx:Application>
So, assuming the user is on Tab 1, and clicks Tab 2, what is happening is the selectedIndex gets changed back to Tab 1 in the change function, but Tab 2 seems to become "dead", so that when the user clicks on Tab 2 again, it doesn't fire a change event.
Something I noticed while trying to figure out the problem, is that on the mouse down event when clicking a tab, the change fires, and the tab changes, but on the mouse up, the tabNavigator seems to come back, at least the tab itself, to the tab that was originally clicked before the selectedIndex was changed.
Anyway, hope this clears up what I'm trying to do.
Thanks!