Combining objects with same Center-Point

I have a drawing with 30.000 shapes. and most of them has another circle right in the middle of other circle. (attached image is only a small part of them).

I am not a VBA programmer but I wrote something but nothing is combined:

Sub combineCircleInCircle()
    Dim kreis As Shape
    Dim s As Shape
    Dim combined As Shape
    Dim xKreis As Double
    Dim yKreis As Double
    Dim xs As Double
    Dim ys As Double
        For Each kreis In ActivePage.Shapes
            kreis.GetPosition xKreis, yKreis
            For Each s In ActivePage.Shapes
                s.GetPosition xs, ys
                    If xs = xKreis And ys = yKreis Then
                    ActiveDocument.CreateSelection s, kreis
                    Set combined = ActiveSelection.Combine
                End If
End Sub