You have not provided much in the way of detail regarding your table structures so I can't provide a precise query, but you would want to do something like
Code:
Dim sSQL As String
sSQL = "UPDATE hardware "
sSQL = sSQL & "INNER JOIN location ON location.user = hardware.user "
sSQL = sSQL & "SET somefield = somevalvue "
sSQL = sSQL & "WHERE somecondition = therightcondition";
DoCmd.RunSQL sSQL