The append operation is just like replace, except that the data passed in the source array or file is appended to the existing data in the control. In the case of array mode, the best way to handle this is to define an array large enough for all the items. For example, you might plan on a maximum of 1000 items, but initially load only 50. If you then append another 75, put them in the array positions from 51 to 125, and specify ARRAY(51) as the array parameter and 75 for the itemcount parameter. This way, your array continues to correspond to the current state of the list, so that you can make sense of the returned selection information.