BLAST Search help

[Lonny R. Levin]

I would like to search among Drosophila genomic sequences submitted to 
Genbank as part of the genome sequencing project for exons 
corresponding to my gene of interest.
What parameters should I use to do a BLAST search
allowing for stretches of 2-300 nucleotides of identity and ignoring
all the homologous genes from other organisms.

thank you.
Lonny Levin
Cornell Medical College