How to: Specify Possible Values for a List Box
The following example fills a ListBox control with the values "Test1", "Test2", and "Test3" when you open the form.
Sub Item_Open()
' Sets the name of page on the form, in this case, the
' Message page on a MailItem form.
Set FormPage = Item.GetInspector.ModifiedFormPages("Message")
' Sets Control to a list box called ListBox1.
Set Control = FormPage.Controls("ListBox1")
' Assign values to the list box.
Control.PossibleValues = "Test1;Test2;Test3"
End Sub