How to find the association between SQL server SPID and domain/mdw logon?

We use ODBC connecting MS Access application (frontend) to MS SQL server 2000 database. Users log on Citrix server to run frontend application. The application share the same ODBC Data Source serverwide. Users logon Citrix server using domain logon and log in Access applcation using login contained in .mdw (workgroup).

MS SQL Enterprise Manager shows which SPID is blocking and which SPID is blocked. What I want to find out which domain user is blocking? In other words, Is there any way to find out which SPID is associated with which domain user or Access login contained in mdw file(not database login)?

Thanks in advance!
Derek