>What is the best way to refresh some textboxes from a value selected from a combobox as soom as a value is selected in the combobox.

You may call from combo.interactivechange event:
Thisform.Textbox.Value=This.Value

>Therefore the combobox does not lose focus but returns to it's original size. Is using a timer the only way.

Sorry, I don't quite follow here.