Modify Default SQL Query for Categories – PLEASE HELP!

Hi All

I haven’t been getting much of a response elsewhere, so Im hoping to get an answer here.

I have a new SQL query that I’d like to use to view categories instead of the default. It will sort based on a custom field. I have the query, I just need to know where to put it so that anytime anyone clicks on a category, this SQL query is used and not the default (which I believe sorts based on the post title).

Can anyone help?

Thanks!
Rob