<<So - a couple of follow-up questions then:
Where do I get a how-to for writing blob filters>>

RTFM? :-),
Seriously though, a few customers have done this, although not many that I
am aware of (please feel free to correct me - any lurkers if I am wrong).
The current docs are terrible on this, it was a known issue, and was meant
to be addressed.
For my sins I have written filters in the past, and do have some source code
(InterBase 3.3 on Sun O/S and C), I suppose it would be feasible for me to
brush this code down and see if it still works, or what I have to do to
correct it to work, and document it, and post the article etc - Whats it
worth?

<<Could I write one in Delphi/Kylix?>>

Probably - it works in the same way as a UDF, sort of. But I would write it
in C, because I like C and C++

Regards
Paul Beach
Main Tel (UK):+44 (0) 1844 354465
Mobile: (UK): +44 (0) 7764 188603
E-mail: pbeach@...