InfoPath 2007 introduces a new control, the multi-select list box, for cases when you want to allow users to select one or more items from the list of options. This list of options may be static, or may come from a data source. For example, you may use a multi-select list box to let the user pick the cities affected by the marketing campaign:
You may also allow users to specify items not on the list by going to Multi-Select List Box Properties, and setting the option to allow users to enter custom values:
Multi-select list box stores data in a repeating field. Every time a user checks an option, a new instance of the repeating field is added; every time an option is unchecked, a field is deleted. This is just like the Bulleted List control.
Let’s analyze the data source at design time, and what goes into the XML when the form is filled out:
Data Source Pane
To specify which (if any) items should be checked in the multi-select list box by default, click Default Values on the Tools menu. Using the marketing campaign example, if you don’t want any option to be selected by default, uncheck the only “city” item:
When you do this, you may see a design-time message that the “Control is bound to a missing field or group”. You can safely ignore this message in this case since the point is to not have any checked by default.
If, instead, you want several options to be checked by default, right-click on the city item, then click “Add another city below”, and specify default values for both cities:
Multi-select list boxes are supported only in InfoPath 2007 client.
– Alex Weinstein