Cancel selection in BoxSelect or ComboBox in ExtJS - extjs

Question

Alhough it sounds as it doesn't make any sense, it does if I get it to work...
What I'm trying to do is get the combo to do nothing, nothing at all... so I managed to stop it from adding the record to the selected records list. But I can't find the way to stop it from painting the item blue.
The best way to understand what I'm trying to do is check the live preview in the ExtJS Docs page, and see how if you select an item in the dropdown list it goes blue although it doesn't add it to the selectedRecords list.
Here is the url to the ExtJS Docs page...
http://docs.sencha.com/ext-js/4-0/#!/api/Ext.form.field.ComboBox
For those of you not familiar with the tool, just look for the Code Editor there, paste this code and click Live Preview.
// The data store containing the list of states
var states = Ext.create('Ext.data.Store', {
fields: ['abbr', 'name'],
data : [
{"abbr":"AL", "name":"Alabama"},
{"abbr":"AK", "name":"Alaska"},
{"abbr":"AZ", "name":"Arizona"}
]
});
// Create the combo box, attached to the states data store
Ext.create('Ext.form.ComboBox', {
fieldLabel: 'Choose State',
store: states,
queryMode: 'local',
displayField: 'name',
valueField: 'abbr',
multiSelect:true,
renderTo: Ext.getBody(),
onListSelectionChange:function(){
console.log('Do nothing');
}
});

Answer 1

Is this what you are looking for?
onListSelectionChange:function(){
this.picker.getSelectionModel().deselectAll();
}
See it working here: http://jsfiddle.net/lontivero/5Ftrf/1/
Update
If you want to keep the previously selected items as they are, you could try with this. It will prevent only new selections.
onListSelectionChange:function(){
var lastSelected = this.picker.getSelectionModel().lastSelected;
itemNode = this.picker.getNode(lastSelected || 0);
if (itemNode) {
this.picker.getSelectionModel().deselect(lastSelected );
}
}
in jsfiddle: http://jsfiddle.net/lontivero/5Ftrf/2/