With this patch, editcombo should accept use of delete and backspace keys.
It also includes a call to a new message when a new item is entered and allownew set to anAsk.
Attached is another patch for the new message called "Accept". This new message might not be relevant, so feel free to modify or even remove it (and change the call from editcombo).
Attached is also a revised version of the combotest demo.