Passing the value of ActiveControl to Unbound Text Box

Similar to the address bar in Excel, I am trying to display the value of the currently entered form field in a Continuous Form in an Unbound Text Box in the Form Header. Here is how I unsuccessfully atempted it:

In the form's OnCurrent Event:

Me.FieldValueDisplay.Value = Me.ActiveControl

What I get on Form Load is an error stating that "The expression you entered requires the Control to be in the active window." After ending the event, tabbing through the fields has no effect, but clicking on them does. Of course, I want the event to work correctly whether clicking into a new field or tabbing into a new field, without having to do an event in each form field (if possible).

Any ideas?