fires after a datatable has collected options
| id | string | the id of the column | 
| data | object | the object that contains options | 
datatable.attachEvent("onCollectValues", function(id, data){
    if (data.values[0].value == "")
    data.values[0].value = "Select something";
});
Assuming you need to filter data via a dedicated popup. Datatable collects the necessary values and populates the popup with them. When all values are colleceted the onCollectValues event is fired.