Ext JS grid wont update for me with this script

The grid wont load the datastore, but if i load the datastore into the grid at the start, it works!

Why? :)

function loadEmployee(id){
 var ds = new Ext.data.Store({
                    autoLoad: true,
                    url: 'query.php?page=4&employee='+id+'&records=10',
                    reader: new Ext.data.XmlReader({
                        record: 'leaverequest',
                    }, ['leave_type', 'employee', 'start_date', 'end_date', 'approver', 'date_requested']),
                    sortInfo: {
                        field: 'employee',
                        direction: "ASC"
                    },
     listeners: {
      'load': function(){
       var grid = Ext.get('leave_history_grid');
       grid.ds = this;
             grid.show();   
             alert("Loaded");      
      }
     }
                    
                });
    
}

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