SHA1 Customized Algorithm

[thedropdead]

Hello Guys,

I will try to keep this Question short.

I am running a GameServer which uses SHA1 Password Encryption.
The Salt of the SHA1 Hash is the Uppercase Username.
I now have a Mysql Database running that i would extract the usernames and the passwords of.
I now want to test the passwords of the Gaming accounts to send users with a weak password an email to change it.

Which would end up in the following short form:
Mysql: SELECT SHA1(CONCAT(UPPER(`username`), ':', UPPER(<pass>)));

Hashcat:
sha1(strtoupper($username).":".strtoupper($pass))

Am i able to somehow implement this Algorithm into Hashcat, and read the username and passwords for the calculating process from a txt file based on username:password?

Thank you for your Support and Help :)