Thanks for your reply. Since yesterday I have done some more research
into TIBOTable. By turning on the SQL monitor it seems as though the
FIndKey method does a sequential scan through the table to find what it
wants. Definitely a time waster. Once you have been all the way
through the table TIBOTable appears to use a cache to retrieve records
which is very fast but not very useful since doing a COMMIT invalidates
the cache.

Looks like I'm going to have to do this the hard way using a TIB_Cursor
and generating my own SQL to make it happen the way I want it to.