Dim ds As New DataSet
Dim da As New OleDbDataAdapter
Dim conStr As String = "SELECT * FROM Main;" & "SELECT * FROM Key;"
Dim conn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data" & _
  "Source=C:\test.mdb;")
Dim cmd As New OleDbCommand(conStr, conn)
da = New OleDbDataAdapter(cmd)
Dim cb As New OleDbCommandBuilder(da)
 
Try
  conn.Open()
  da.Fill(ds)
  conn.Close()
  MsgBox("Datenbank erfolgreich geladen!")
Catch ex As Exception
  MsgBox("Es trat ein Fehler beim Öffnen der Datenbank auf!" & vbNewLine &  _
    ex.Message, , "Fehler")
End Try