The following VBA example creates a blend between a circle and a polygon, and specifies the key nodes on the two shapes that the blend uses as starting points of the shapes.
Sub Test()
Dim s1 As Shape, s2 As Shape, eff As Effect
Set s1 = ActiveLayer.CreateEllipse2(2, 9, 1)
Set s2 = ActiveLayer.CreatePolygon(4, 3, 6, 5, 5)
s1.Fill.UniformColor.RGBAssign 255, 0, 0
s2.Fill.UniformColor.RGBAssign 255, 255, 0
Set eff = s1.CreateBlend(s2)
With eff.Blend
.MapNodes = True
.StartPoint = s1.SnapPoints.Edge(4, 0)
.EndPoint = s2.SnapPoints.Edge(1, 0)
End With
End Sub