Private Declare Function GetUserName _
                Lib     "advapi32.dll" _
                Alias   "GetUserNameA" ( ByVal lpBuffer As String, _
                                               nSize    As Long _
                                       ) As Long

    .  .  .


    Dim lngCnt  As Long
    Dim lngRtrn As Long
    Dim sUserNm As String * 150

    lngRtrn = GetUserName(sUserNm, 149)
    lngCnt  = InStr(sUserNm, Chr$(0))

    If lngCnt < 2 Then
        MsgBox "No UserName obtained."
    Else
        sUserNm = Left$(sUserNm, lngCnt - 1)
        MsgBox "UserName = """ & sUserNm & """"
    End If