XmListDeletePos man page
XmListDeletePos — A List function that deletes an item from a list at a specified position
#include <Xm/List.h> void XmListDeletePos( Widget widget, int position);
XmListDeletePos deletes an item at a specified position. A warning message appears if the position does not exist.
Specifies the ID of the List from which an item is to be deleted.
Specifies the position of the item to be deleted. A value of 1 indicates that the first item in the list is deleted; a value of 2 indicates that the second item is deleted; and so on. A value of 0 (zero) indicates that the last item in the list is deleted.
For a complete definition of List and its associated resources, see XmList(3).