Help with cryptext hash: sha1($pass.sha1($pass))

Hello.

I've a sort of files crypted in 2004 with this utility from Nick Payne.
I don't remember the password, but I've a pattern for it (and a charset for hashcat)
As I've a backup of my user data I have the password hash stored in the registry. as I don't remember to have changed this password, I presume that it's "the password".

I tried hashcat witouth success and, reading some documentation, I've found that the stored password is a two steps hash. The algorithm would be like this: sha1($pass.sha1($pass)) that isn't in the algorithm list of hashcat.

And the question is: Can I define this algorithm? (I think no).
If not, how can I generate a dictionary using my charset? (probably statsprocessor).
Because there is a simple code to decrypt files that can be adapted for comparing hashes (It will be slower than hashcat, but...)

Regards,

Javier