man XmListSelectPos (3): A List function that selects an item at a specified position in the list

SYNOPSIS

#include <Xm/List.h>
void XmListSelectPos(
Widget widget,
int position,
Boolean notify);

XmListSelectPos highlights a List item at the specified position and adds it to the list of selected items.

widget: Specifies the ID of the List widget.
position: Specifies the position of the item to be selected. A value of 1 indicates that the first item in the list is selected; a value of 2 indicates that the second item is selected; and so on. A value of 0 (zero) indicates that the last item in the list is selected.
notify: Specifies a Boolean value that when TRUE invokes the selection callback for the current mode. From an application interface view, calling this function with notify True is indistinguishable from a user-initiated selection action. When notify is FALSE, no callbacks are called.

For a complete definition of List and its associated resources, see XmList(3).