ExtJS 4 - Grid cell events?

I think the key to your question lies in the Selection Model chosen for the grid. The default is row selector so the item select events operate on rows. Check out cell selector API here: http://docs.sencha.com/ext-js/4-0/#!/api/Ext.selection.CellModel-event-select

(ExtJS 4.1)

You could also hook on the (undocumented) uievent of the grid's view:

grid.getView().on( 'uievent', this.onUIEvent, this);

onUIEvent: function ( aType, aView, aCell, aRecordIndex, aCellIndex, aEvent )
{
    console.log( aRecordIndex + ' : ' + aCellIndex );
},