dynamically set combobox's hidetrigger config option

[sunjiankirk]

I want to change the config options of one combobox
according to the choice of another.

however the change doesn't happen

var com_Department = new Ext.form.ComboBox({
            fieldLabel:'name',
            hiddenName:'m_department',
            store:ds_departmentList,
            triggerAction: 'all',
            displayField:'department',
            valueField:'id',
            editable:true

                                                });            
 var com_departmentType = new Ext.form.ComboBox({
            fieldLabel:'type',
            store:ds_departmentType,
            hiddenName:'temper',
            displayField:'type',
            valueField:'id',
            mode:'local',
            triggerAction: 'all'
            ,listeners:{
                'select':function(combo,record,index)
                        {
                            if(index == 0)//I need normal combobox
                            {
                                   combo.hideTrigger:true,
                                  ....
                            }
                            else
                            {
                                  combo.hideTrigger:false,
                                  ...
                            }
                        }
                    }
                                                });

[sunjiankirk]

in fact , I want to display different style of component
one is normal combobox
the other looks like textfield