Are you trying to set all the blank userfields in the Contact Log table to the same userid? If so, create an update query against the Contact Log table and just define the userid to go into the userfield:
UPDATE [Contact Log ]SET [user] = "rlj";
More importantly, it sounds as if you are trying to assign a particular contact log record to a user and haven't set up your relationship yet. If you enter the relationships window and add the two tables, make sure a line is draw from the user field in each of the tables. You may also want to right-click this relationship line and check your cascade effects, so that if you update a userid in the Users table, it will update all the records in the Contact Log table as well.
You will not be able to create this join in the relationship window until you have completed the update query above. This will assign ALL the Contact Log records to that one user, but you can then go in and update them as necessary. May be a pain, but unless you have some other criteria somewhere to determine who "owns" each record, this is your best bet. But the relationship setup will prevent this going forward. This may also require modifying the entry forms a bit, depending on how they are currently setup.
Good luck and let us know if we can help further
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People think it must be fun to be a super genius, but they don't realize how hard it is to put up with all the idiots in the world. (Calvin from Calvin And Hobbs)
Robert L. Johnson III
CCNA, CCDA, MCSA, CNA, Net+, A+, CHDP
VB/Access Programmer