'Determine if a user belongs to a specific group
Public Function IsUserInGroup (strUser As String, _
        strGroup As String) As Boolean
    Dim wrk As DAO.Workspace

    Set wrk = DBEngine(0)
    On Error Resume Next

    IsUserInGroup = False

    'Check in the Users --> Groups collection
    IsUserInGroup = _
         (wrk.Users(strUser).Groups(strGroup).Name = strGroup)

    'You can also do it this way...
    'Check in the Groups --> Users collection
    'IsUserInGroup = _
         (wrk.Groups(strGroup).Users(strUser).Name = strUser)

    Set wrk = Nothing
End Function