The DataSource property uses the ADO/DAO record set objects. Use the PutItems to load an array to the group. The following sample binds an ADO recordset to an ExplorerTree group:

With ExplorerTree1.Groups.Add("Group 1")
    Set rs = CreateObject("ADODB.Recordset")
    rs.Open "Orders", "Provider=Microsoft.Jet.OLEDB.3.51;Data Source= D:\Program Files\Microsoft Visual Studio\VB98\NWIND.MDB", 3 ' Opens the table using static mode
    .BeginUpdate
    .ColumnAutoResize = False
    .HeaderVisible = True
    Set .DataSource = rs
    .EndUpdate
End With

The DataSource clears the columns collection, and fill the record set into the group, like a list. Use SetParent method to make your list a hierarchy.