XmListDeleteItems man page
XmListDeleteItems — A List function that deletes items from the list
#include <Xm/List.h> void XmListDeleteItems( Widget widget, XmString *items, int item_count);
XmListDeleteItems deletes the specified items from the list. For each element of items, the first item in the list that matches that element is deleted. A warning message appears if any of the items do not exist.
Specifies the ID of the List from whose list an item is deleted
Specifies a pointer to items to be deleted from the list
Specifies the number of elements in items This number must be nonnegative.
For a complete definition of List and its associated resources, see XmList(3).