Apparently you cannot disable a command button. Is it normal to write code to cancel the on click event if a forms control has data (is not null) or in the case of a date/time field > 0 ?
Hmm, when a command button is disabled, it should turn gray (I think). Did yours do that? If not, maybe it isn't disabled. Also, you can verify if it's disabled or not by checking its Enabled property using code. Just a thought...
You can just set its Enabled property to False
If your command button is named MyCommand, then it's
Me.MyCommand.Enabled=False
You can also use the Visible property to hide or unhide the button.