Use the BeginUpdate and EndUpdate methods to avoid drawing the control while adding multiple groups. Use the group's BeginUpdate and EndUpdate method to maintain performance while adding new items to the group's list.

For instance, the following sample shows how to use the BeginUpdate and EndUpdate methods:

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
With ExplorerTree1
    .BeginUpdate
        With .Groups.Add("Group 1")
            .BeginUpdate
                .ColumnAutoResize = False
                .HeaderVisible = True
                With .Columns
                    .Clear
                    For Each f In rs.Fields
                        .Add f.Name
                    Next
                End With
                .PutItems rs.GetRows()
            .EndUpdate
        End With
        With .Groups.Add("Group 2")
            .BeginUpdate
                .PutItems Array("Item 1", "Item 2", "Item 3")
            .EndUpdate
        End With
    .EndUpdate
End With