In the AfterUpdate event of the check box try something like:
Me.NameOfOtherControl.Enabled = Me.NameOfCheckBox.Value
This will enable the other control if the checkbox is true (checked) and
disable it if the checkbox is false (not checked). Make sure that the
checkbox can't have a Null value for this to work. If it can, you can do the
above with an If statement instead
If Me.NameOfCheckbox = True Then
Me.NameOfOtherControl.Enabled = True
Else
Me.NameOfOtherControl.Enabled = False
End If
If the value of the checkbox is to be remember (i.e. it is bound to a field
in the underlying table) then you will also need to place the above code in
the form's Current event.