[Closed] Undo Context Not Appearing in Stack

Hi Guys,

I have written a very simple (and clumsy) little macro here, to demonstrate my problem. Sometimes when I am using the undo clauses, they are not storing an undo in my stack!

Here is an example of a clumsy macro to flatten a spline. From the code I would have hoped that it would have given me a “Spline Flatten” addition to my undo stack. But it doesnt record anything at all! I am sure I am doing something pretty silly. Is it anything to do with the on execute context?

macroScript SplineFlat category:"SplineFun"
(

on execute do
	(
	undo "Spline Flatten" on
		(
		SelSplines = for o in selection where (iskindof o line) or (iskindof o SplineShape) collect o

		for o in SelSplines do	
			(
			for s = 1 to numsplines o do 
				(
				for i = 1 to (numknots o s) do 
					(
					SpPos = getknotpoint o s i
					setknotPoint o s i [SpPos.x,SpPos.y,0] 
					
					)--End of for
				)
			updateshape o
			)--End of for
		)--End of Undo
	)--End of Execute
	
)--End of SplineFlat

Any ideas why this doesnt record in the stack? Does it have to be from a rollout or something? I am in Max 2009.

Thanks for your time guys,

Rich