fires before a cell is selected
| selection | object | the selected object | 
| preserve | boolean | indicates whether the previous selection will be saved | 
| boolean | returning `false` will prevent item selection | 
some.attachEvent("onBeforeSelect", function (selection, preserve){
    // ... some code here ...
    // return false to block operation
    return true;
});
The selection object depends on the selection mode and includes the following attributes: