This example changes all straight segments to curved segments in shape three on myDocument
. Shape three must be a freeform drawing.
Set myDocument = Worksheets(1)
With myDocument.Shapes(3).Nodes
n = 1
While n <= .Count
If .Item(n).SegmentType = msoSegmentLine Then
.SetSegmentType n, msoSegmentCurve
End If
n = n + 1
Wend
End With