SuperBoxSelect : selection problem

[Micrasoft]

Hi everybody,

I try to developp a simple Extra for modx. So i use extjs 3. I would like to populate a SuperBoxSelect with some values with a store :

Moinsdedechets.SuperBoxSelect = function (config) {
    config = config || {};
    Ext.applyIf(config, {
    xtype:'superboxselect'
        ,triggerAction: 'all'
        ,mode: 'remote'
        ,fields: ['id', 'nom_activite']
        ,displayField: 'nom_activite'
        ,valueField: 'id'
        ,store: new Ext.data.JsonStore({
            id:'id'
            ,autoLoad: true
            ,root:'results'
            ,fields: ['id', 'nom_activite']
            ,displayField: 'nom_activite'
            ,valueField: 'id'
            ,url: Plugin.config.connectorUrl
            ,baseParams: {
                action: 'mgr/plugin/getlistactivites'
            }
        })
        ,emptyText: "Choisissez des activités"
        ,forceSelection : true
        ,listeners : {
            render : function(sbs){
                sbs.wrapEl.on('load', function(ev,h,o){
                    
                
                },sbs,{
                    delegate : 'li.x-superboxselect-item'
                });
            }
            }
    });
    Moinsdedechets.SuperBoxSelect.superclass.constructor.call(this, config);


};
Ext.extend(Plugin.SuperBoxSelect, Ext.ux.form.SuperBoxSelect);
Ext.reg('combo-activites', Plugin.SuperBoxSelect);

And then, I add this element in my grid :

        ,{
            xtype: 'combo-activites'
            ,fieldLabel: _('plugin.activite')
            ,name: 'nom_activite[]'
            ,width: 200
        }

This code works well. But now, I would like to preselect items relative to a record id. How can I do that? With a second store, but how ?

Thank you for your answers and sorry for my english.

[mitchellsimoens]

Where did the superboxselect come from?