in the Valid I keyed

this.value = this.DisplayValue
this.requery()

Try this instead:

Change the RowSourceType of the ComboBox to 0-None and populate it like this in its Init():

WITH This
  .AddItem( [Apples] )
  .AddItem( [Oranges] )
  .AddItem( [Pears] )
ENDWITH

And use this code in its Valid():

WITH This
  IF NOT EMPTY( .DisplayValue ) AND .ListIndex = 0
    .AddItem( .DisplayValue )
    .Requery()
  ENDIF
ENDWITH