Use the Items property to access the group's Items collection. Use the Items collection to add, remove or change the group items. Use the GetItems method to get items collection into a safe array. Use the PutItems method to load items from a safe array. 

The following VBA sample enumerates all groups and items being shown on the control:

Dim e As EXPLORERTREELib.ExplorerTree
Set e = ExplorerTree1.Object
With e
    Dim g As EXPLORERTREELib.Group
    For Each g In .Groups
        Debug.Print "Enumerate Group " & g.Caption
        For Each i In g.Items
            With g.Items
                Debug.Print "Item " & .CellCaption(i, 0)
            End With
        Next
    Next
End With

The following VBA sample enumerates all groups and items being checked on the control:

Dim e As EXPLORERTREELib.ExplorerTree
Set e = ExplorerTree1.Object
With e
    Dim g As EXPLORERTREELib.Group
    For Each g In .Groups
        Debug.Print "Enumerate Group " & g.Caption
        For Each i In g.Items
            With g.Items
                If Not (.CellState(i, 0) = 0) Then
                    Debug.Print "Item " & .CellCaption(i, 0)
                End If
            End With
        Next
    Next
End With