Function BlockInsert(Offset:LongInt;Data:Pointer;Size:Word):Word;

    This inserts a block  of  data  (pointed  to  by  Data)  of size Size
    into  the  current  database  at   offset   Offset.   This  does  not
    affect the directory of  the  database  and  is thus not usually used
    by the users, it is rather for internal usage.

    As this uses swap files it is  a  little  slow,  but  I think that is
    unavoidable.  Use a disk cache to improve performance.