Sub TestSub()
Dim oDoc As Inventor.Document
Dim oCD As PartComponentDefinition
Dim oDerivedPtComps As DerivedPartComponents
Dim oDocDescr As DocumentDescriptor
Set oDoc = ThisApplication.ActiveDocument
Set oCD = oDoc.ComponentDefinition
Set oDerivedPtComps = oCD.ReferenceComponents.DerivedPartComponents
Debug.Print oDerivedPtComps.Item("1").Name
End Sub