For those items that are to be disabled, you could add a new style class to each cell control to indicate it's disabled. You could use a formatter function:
...
addStyleClass : { parts : [ 'isRecordLocked' ], formatter : function(isRecordLocked) { return isRecordLocked ? "disabledStyle" : ""; }
},
...where 'isRecordLocked' is the indicator in your data whether your record is locked, and 'disabledStyle' is the custom CSS class which caters for a disabled look of your cell.
If you need to suppress any press events for the locked records, you could do it in the same way.