Disabling the some checkboxselectionmodel based on the condition

[SharmilaUmasankar]

Hi

Am trying to disable some checkboxselection model inserted in grid .I have tried with the beforerowselect listener of the checkboxselection .

    var checkbox= new Ext.grid.CheckboxSelectionModel({
                listeners: {
                "beforerowselect" : function (sm, rowIndex, keep, rec) {
                var id = parseInt(rec.id);
                 if (id=='24'){
                 return false;
                }
                }
                }
                });
                coumns1.push(checkbox);

This listener is not triggered when the row is selected.Is there anyway to disable the checkboxselection model based on some criteria?