Nested Xrefs

How can I tell if an xref is nested within an xref, within an xref, etc... by using GetEntity???
Here's what I'm working with right now.

Public Sub PickXref()
Dim Entity As AcadEntity
Dim Point As Variant
Dim BLK As AcadExternalReference

On Error Resume Next
Do
ThisDrawing.Utility.GetEntity Entity, Point, "Select Xref: "
If Err.Number <> 0 Then
ThisDrawing.SendCommand "_vbaunload" & vbCr & """PickXref.dvb""" & vbCr
Exit Do
Else
If TypeOf Entity Is AcadExternalReference Then
Set BLK = Entity
' How can I determine if this Xref has nested xrefs and so on and so forth?!?
End If
End If
Loop
End Sub

TIA!