blastlocal returns an error

I try to blast against a local database that i've created, but blastlocal keeps returning an error (unable to open 'mydatabase.nin'. How do i create this file/where do i find it?

------ Here is the script for creating database/blasting and the output i get:

blastformat('Inputdb', 'trimmedcores.fasta','Title', 'mydatabase'); BlastRes=blastlocal('InputQuery', 'myotus.fasta', 'Database', 'mydatabase', 'Program', 'blastn');

Error using blastlocal (line 294) BLASTALL produced the following error(s): BLASTN 2.2.17 [Aug-19-2007]

[NULL_Caption] WARNING: Unable to open mydatabase.nin [NULL_Caption] WARNING: OTU_4: Unable to open mydatabase.nin