When autocomplete is making a suggestion after keying in a character, the suggested portion is highlighted in blue. Is there some way I can determine what the user actually keyed vs. the suggested portion in the textbox?
Well, you can determine what text in the Combo is selected using the SelectionStart and SelectionLength properties.
Other than that, you would have to trap the Key messages and track them yourself. There's nothing in the control that keeps track of this.