I apologize again, the only disabling property for the CheckBox is locked.
' Set the checkbox's default value to Locked = Yes, in form design view, under
' the properties, Data tab.
' The names here refer to = Yes_No is the ComboBox
' Check_Box = CheckBox
' I copied the code from my test and if you use it, you'll have to rename the
' controls to the names you've given.
Private Sub Yes_No_AfterUpdate()
If Me!Yes_No = "No" Then
Me!Check_Box.Locked = True
Me!Check_Box.Locked = False
' Clears the value of the checkbox
Private Sub Yes_No_Enter()
Me!Check_Box = False
' If you clear the form the Check_Box's Locked state must be reset to Yes.
Check the event properties of the combo box. Under On Enter and After update, it should display [Event Procedure]. This means that it is linked to the code. In any case, click on these event procedures just to see that you end up in the correct procedure. When you click on the right of the event procedure and it creates a new Sub, this means that you have a control naming error in the procedure. In this case, you will have to correct it. Also, bear in mind that the words Yes_No and Check_Box are my references, used as an example and you have to use the control names you've given.