You can use the PreviousControl property with the Screen object to return a reference to the control that last received the focus.
Setting
The PreviousControl property contains a reference to the control that last had the focus. Once you establish a reference to the control, you can access all the properties and methods of the control.
This property is available only by using a macro or Visual Basic and is read-only.
Remarks
You can't use the PreviousControl property until more than one control on any form has received the focus after a form is opened. Microsoft Access generates an error if you attempt to use this property when only one control on a form has received the focus.