Using con As New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data" & _
  "Source=C:\mydatabase.mdb;")
   con.Open()
   Using com As New OleDb.OleDbCommand("SELECT Count(meinPrimaerfeld) AS" & _
     "AnzahlVonDatensaetzen FROM meineTabelle", con)
     Dim reader As OleDb.OleDbDataReader = com.ExecuteReader
     If reader.HasRows Then
        Do While reader.Read()
            MessageBox.Show(reader.GetInt64(0))
        Loop
     End If
   End Using
End Using