'Assign Bigger to a shape. Note that if the shape's LockAspectRatio
'is set to true, this will make the shape bigger or smaller twice as
'much as expected.

'If the shape was small, make it bigger, and set its action
'to run the Smaller macro.
Sub Bigger(myShape As Shape)
    myShape.Height = myShape.Height * 1.5
    myShape.Width = myShape.Width * 1.5
    myShape.ActionSettings(ppMouseClick).Run = "Smaller"
End Sub

'If the shape was big, make it smaller, and set its action
'to run the Bigger macro.
Sub Smaller(myShape As Shape)
    myShape.Height = myShape.Height / 1.5
    myShape.Width = myShape.Width / 1.5
    myShape.ActionSettings(ppMouseClick).Run = "Bigger"
End Sub