Guidance Needed for Populating 'Colleague Name' Field from Leads

Hi team, I need some help setting the “colleague_name” field. I have a list of around 3,000 rows, where in many cases multiple leads belong to the same company. What I’m trying to do is populate a column called “colleague_name” with the first name of another lead from the same company (matched by domain), making sure it doesn’t use the same first name as the current record. Has anyone done something similar before, or have any tips on how to approach this? I’d really appreciate any guidance. Thanks in advance!