warning: unable to bind to property 'ext' on class 'XML' (class is not an IEventDispatcher)
It's coming from:
<mx:FormItem label="Ext" required="true" includeInLayout="false">
<mx:TextInput id="ext"
focusOut="c.formatNumbers(ext, salesreps)" width="10%"
text="{salesreps.selectedItem.ext}"
restrict="0-9"/>
</mx:FormItem>
where salesreps is a DataGrid with an XML as a dataProvider.
Any idea?

