Dim catDB As ADOX.Catalog
Dim cnnDB As ADODB.Connection

Set cnnDB = New ADODB.Connection
cnnDB.ConnectionString =  "Provider=Microsoft.Jet.OLEDB.4 . 0 ;" & _
                          "Data Source=C:/MyDB.mdb;"  & _
                          "Jet OLEDB:System Database=C:/MyWrkGrp.mdw;"  & _
                          "User ID=Admin;Password=Admin;" 
cnnDB.Open

Set catDB = New ADOX.Catalog
Set catDB.ActiveConnection = cnnDB

MsgBox catDB.Tables.Item( "tblOrders" ).Columns.Count
'          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Это работает

MsgBox catDB.Groups.Count
'          ^^^^^^^^^^^^ а это выдает: 
'Run time error '3251'. Object or Provider is not capable of performing requested operation