What Jimatqsi has posted would definitely work.
You could take it a little further if you like and when the user clicks whatever button they click to login, store the User Name/ID into a Global Variable.
You could then create a function, to return the UserID.
- Public Function getUserID() As String
-
getUserID= gUserID
-
End Function
Lastly, on Forms where you want to fill in the User as the Default, set the Default Property of the User Field to the new function.