get Parent value from Child

I use the Parent property in the TreeNode often to find the Text of the Parent of a particular TreeNode in a TreeView. Is it possible to mimic this functionality with a custom class.

I have a class called clsSummary and it contains a collection of classes called colDetail whilch is based on a class called clsDetail. Is there a way to access a value in the parent (clsSummary) from the child (clsDetail)? Any suggestions are appreciated.

clsDetail.Quantity = clsDetail.Parent.Quantity

So...
clsSummary contains a collection of class clsDetail.
I added another object to the clsDetail class of type clsSummary.
When I add a clsDetail to the clsSummay.colDetail collection I set the value for the "parent" so I can reference it like:

clsDetail.clsSummary.Quantity = 0

Is that wastefull? It should just be a reference to a place in memory right? So I'm not storing duplicate information... Some feedback would really be appreciated. If I've been unclear let me know.

Here is some code...
Is it ok for a child to have a copy of the Parent?
It seems like this is circular reference...

VB Code:

Private Class clsSummary
    Public Property Quantity As Integer
    Public Property Detail As clsDetail ' [Actually a collection in my code]
End Class
Private Class clsDetail
    Public Property Quantity As Integer
    Public Property Parent As clsSummary ' <-- Reference to Parent class...
End Class

The .NET Framework has circular references in it...so it must work. And yeah, you're not making a copy of the data, it's just a referene.