Error connecting to MySQL using VBA (3709 error)

[Matheus Faria]

Hi all,
Below is a code that will run every time a particular excel file is opened in order to block unauthorized access.
For this the idea is to check the motherboard serial of the computer and verify if it is registered in a mysql database. If it is not registered it closes the file and otherwise autorize the access.
The Workbook_Open function is responsible for autorize or block the access.
The MBSerialNumber function takes the serial of the motherboard.
The ConnectDB function accesses and performs a search of the MySQL database verifying if the serial of the computer is registered.

At this last function I'm having error 3709 (line 4 from bottom to top). I would like your help to solve this problem.

 Public cn As Variant
  Private Sub Workbook_Open()
     Call MBSerialNumber
     Call ConnectDB
     If rs < 1 Then
         MsgBox ("Data Security failier, This workbook will close")
         ActiveWorkbook.Save
         ActiveWorkbook.Close
     End If
  End Sub
  Public Function MBSerialNumber() As String
     Dim objs As Object
     Dim obj As Object
     Dim WMI As Object
     Dim sAns As String
     Set WMI = GetObject("WinMgmts:")
     Set objs = WMI.InstancesOf("Win32_BaseBoard")
     For Each obj In objs
         sAns = sAns & obj.SerialNumber
         If sAns < objs.Count Then sAns = sAns & ","
     Next
     MBSerialNumber = sAns
  End Function
  Private Sub ConnectDB()
     Set cn = CreateObject("ADODB.Connection")
     cn.Open "DRIVER={MySQL ODBC 5.3 ANSI Driver};" & _
         "SERVER=xxx.xxx.xx;" & _
         "DATABASE=xxx_xxx;" & _
         "USER=xxxx_xxx;" & _
         "PASSWORD=xxxxxxx"
     Set rs = CreateObject("ADODB.Recordset")
     rs.Open "SELECT COUNT(serial) FROM users WHERE serial='" & MBSerialNumber & "', cn, adOpenStatic, adLockOptimistic"";"
     cn.Close
     Set cn = Nothing
  End Sub