extJS and HTML select

Hi All-

I have two select dropdowns. When one dropdown is selected, the other dropdown value selected to a default value which is 0 in my case and viceversa. We had to convert our dropdowns to extJS combobox to include search functionality in the dropdown. How can I achieve the above in extJS. In javascript I can simply use onchange function and get what I want, but not able to do the same in extJS.

Here is the code I have till now
Ext.onReady(function(){
  var converted = new Ext.form.ComboBox({
     typeAhead: true,
     triggerAction: 'all',
     transform:'id_Select1',
     width:600,
    forceSelection:true,
    emptyText:'Select' }
});

var converted2 = new Ext.form.ComboBox({
     typeAhead: true,
     triggerAction: 'all',
     transform:'id_select2',
     width:600,
     forceSelection:true,
     emptyText:'Select'
});
}); I have two select drop downs populated from database