Highlight a Item from a Listbox in app designer

Hi, I want to select a Item from a list box and when I push a button, this Item has to highlight.

When I push the button all the list box changed the color, I dont know how can I do it for only one item.

How can I change the properties of a Item without change the rest of items of the list box?

[Geoff Hayes]

Ethan - please post your button callback code that shows how the list box is being updated so that we can get an idea as to why all items are being selected. Presumably all you need to do is just set the Value property to a valid item in the list. Something like

app.myListbox.Value = 'apple';

where "apple" is a valid selection in the list box set of items.