How to select an option in a jQuery ui selectmenu dynamically?

After changing a menu from a regular select to a jQuery selectmenu, I can no longer select options in it programatically. Is there a way to do this?

The code to select is (assuming ListId is the actual Id of the list)

$('#ListId').val(value);

The plugin is activited like this:

$("#ListId").selectmenu({ style: "dropdown", width:140 });

Is there a way to select an item in the select menu? Calling the same .val(value) function just selects the value in the hidden original select list, not the nicely styled jQuery selectmenu.

$('#ListId').selectmenu("value", value);