I am not sure if exactly what you're describing is possible, without using some additional plugins. Do you mean that you added a Custom profile field, and you want to filter what students are displayed in the Grader report, based on the custom profile field?
It is possible to do some filtering on the Grader report based on Groups. That would probably require you to rethink your workflow, though.
For example, you might be able to achieve something like this with a combination of Cohorts, Groups, and this Cohort members to group plugin.
If you can describe your situation a little more, I might have some other ideas.