Can't actually see anything wrong with it. The only thing I would say is that the dot operator should be a bang (!) operator and, are the field names the same in both tables?. If all else fails, delete the command button and create from scratch.
The difference is the ! operator indicates that what follows is a user-defined item (an element of a collection). For example, use the ! operator to refer to an open form, an open report, or a control on an open form or report.
The . (dot) operator usually indicates that what follows is an item defined by Microsoft Access. For example, use the . (dot) operator to refer to a property of a form, report, or control.
You may not see any problem, but it one of those insidious little rascals that, if code that has been working perfectly normally up til now, suddenly gives up. In my view, it is better to be safe than sorry later.