To determine which workstation a user logs in from you would need to scan the security event log on each domain controller. There is 3rd party software that can do this for you and aggregate it, but you would spend a lot of time trying to do this manually.
To start with you will need to increase the log size of your security logs on the domain controllers so they can store the logs until you have time to scan them. These 3rd party applications do this scan on a scheduled basis and you usually size the log big enough to give the application time to complete the scan before events get overwritten. Depending on the size of your environment you could be scanning logs once a day or every hour.
In short, there is no field in Active Directory that stores this information. Even the last logon time field is unique to a User Object on each Domain Controller.