Populate attribute with list of Server Names

I am trying to build a Workflow for User Logon restrictions. I need the workflow to search for servers that exist in different groups, OU's or managed Unit. If necessary i can consolidate them into 1. The issue is I need to then populate the user attribute "userWorkstation" found in another search  with all the server names found with a Semicolon in between each.


Server1;Server2;Server3;   etc...