Highlight an UltraCombo when entry not in list

I have an UltraCombo that is populated from a UD table when the form loads. The UltraCombo control has its LimitToList property set to true, to keep people from editing it.

If the text entered does not match an item in the combo’s list, you cannot leave the field - neither by tabbing to, or clicking another control . This isn’t always obvious, so it sometimes looks like the form has crashed.

How can I highlight the filed if the text isn’t in the list?

I assume it would be using the ValueChanged event, and set the style to Warining. But how do I compare Value against the combo’s list. Or is there a property to indicate that it IS in the the list? (Nothing jumped out at me in the UltraCombo’s Object Explorer).

FWIW, this combo already has a warning (made via Rule Wizard) to highlight the field when it is null.

UltraCombo.DropDownStyle = UltraComboStyle.DropDownList; <-- Only allows selecting an item from the list, no typing.

Thanks.

But I get
Error: CS0103 - line 109 (627) - The name 'UltraComboStyle' does not exist in the current context

Do I need to add a using ... ?

using Infragistics.Win.UltraWinGrid;

Thanks. Tried a few, but would have never went with UltraWinGrid

Now that I look at the Object Explorer again I see it.