Table: [CurrentConnections]
computerName  Text(255), Primary Key

Table: [ConnectionLog]
computerName  Text(255), Primary Key
userName      Text(255)

Public Sub GetCurrentlyConnectedMachines()
    Dim cdb As DAO.Database, rst As DAO.Recordset
    Dim fso As Object  '' FileSystemObject
    Dim lck As Object  '' ADODB.Stream
    Dim lockFileSpec As String, lockFileExt As String, tempFileSpec As String
    Dim buffer() As Byte

    Set cdb = CurrentDb
    cdb.Execute "DELETE FROM CurrentConnections", dbFailOnError
    Set rst = cdb.OpenRecordset("SELECT computerName FROM CurrentConnections", dbOpenDynaset)

    lockFileSpec = Application.CurrentDb.Name
    If Right(lockFileSpec, 6) = ".accdb" Then
        lockFileExt = ".laccdb"
    Else
        lockFileExt = ".ldb"
    End If
    lockFileSpec = Left(lockFileSpec, InStrRev(lockFileSpec, ".", -1, vbBinaryCompare) - 1) & lockFileExt

    '' ADODB.Stream cannot open the lock file in-place, so copy it to %TEMP%
    Set fso = CreateObject("Scripting.FileSystemObject")  '' New FileSystemObject
    tempFileSpec = fso.GetSpecialFolder(2) & "" & fso.GetTempName
    fso.CopyFile lockFileSpec, tempFileSpec, True

    Set lck = CreateObject("ADODB.Stream")  '' New ADODB.Stream
    lck.Type = 1  '' adTypeBinary
    lck.Open
    lck.LoadFromFile tempFileSpec
    Do While Not lck.EOS
        buffer = lck.Read(32)
        rst.AddNew
        rst!computerName = DecodeSZ(buffer)
        rst.Update
        buffer = lck.Read(32)  '' skip accessUserId, (almost) always "Admin"
    Loop
    lck.Close
    Set lck = Nothing
    rst.Close
    Set rst = Nothing
    Set cdb = Nothing
    fso.DeleteFile tempFileSpec
    Set fso = Nothing
End Sub

Private Function DecodeSZ(buf() As Byte) As String
    Dim b As Variant, rt As String
    rt = ""
    For Each b In buf
        If b = 0 Then
            Exit For  '' null terminates the string
        End If
        rt = rt & Chr(b)
    Next
    DecodeSZ = rt
End Function

Private Sub Form_Load()
    Dim cdb As DAO.Database, rst As DAO.Recordset
    Dim wshNet As Object  '' WshNetwork

    Set wshNet = CreateObject("Wscript.Network")
    Set cdb = CurrentDb
    Set rst = cdb.OpenRecordset("SELECT * FROM ConnectionLog", dbOpenDynaset)
    rst.FindFirst "ComputerName=""" & wshNet.computerName & """"
    If rst.NoMatch Then
        rst.AddNew
        rst!computerName = wshNet.computerName
    Else
        rst.Edit
    End If
    rst!userName = wshNet.userName
    rst.Update
    Set wshNet = Nothing
End Sub

SELECT CurrentConnections.computerName, ConnectionLog.userName
FROM CurrentConnections LEFT JOIN ConnectionLog
    ON CurrentConnections.computerName = ConnectionLog.computerName
ORDER BY ConnectionLog.userName;

Private Sub Form_Load()
    UpdateFormData
End Sub

Private Sub cmdRefresh_Click()
    UpdateFormData
End Sub

Private Sub UpdateFormData()
    GetCurrentlyConnectedMachines
    Me.Requery
End Sub

Private Sub Form_Unload(Cancel As Integer)
Dim wshNet As Object
Dim deleteSQL As String

Set wshNet = CreateObject("WScript.Network")
        DoCmd.SetWarnings False
        deleteSQL = "DELETE tblCurrentConnections.* " & _
        "FROM tblCurrentConnections WHERE[computerName] = '" & wshNet.computerName & "';"
                DoCmd.RunSQL deleteSQL
        DoCmd.SetWarnings True
End Sub