If dlgitem is a outline list item in window, this function selects the entry row that has application data that matches either start or end (when supplied).

If dlgitem is a textbox control (or an editable combobox control) in window, dlgitem_set_selection highlights a range of text in the text field starting at position start and ending at position end. If end is not supplied, the highlighting continues to the end of the text. If start and end are the same, no text is highlighted and the cursor is placed at that position.

If dlgitem_set_selection is called with any other type of dialog box item, it returns 0 and sets $ERROR. Otherwise, the function returns 1.