do you now a udf function i can declare in firebird 1.5 ?

i would like to find some data by searching on a date field format.

i would like to extract all data for a periode,
for example a periode from 12 july to 24 september.
of course i want the query to return data for all years.

i can do it by shaking month + day function,
but it would be more difficult to do.

Thanks,
Julien