Select editable spline sub-objects

Here's a great plugin for managing subobject selections and material IDs for editable splines.

SubSpline: http://www.splinedynamics.com/subspline/

If I understood it right, I add a Edit Spline modifier, enter desired sub-object mode and then press the select button in the dialog.

If so - nothing happens. How comes?

(
	global rol_selEveryNthSubSpline
	try(destroyDialog rol_selEveryNthSubSpline)catch()
	rollout rol_selEveryNthSubSpline "Select N-th Sub-Spline"
	(
		spinner spn_Nth "N-th" range:[1,1000000,2] type:#integer
		button btn_select "SELECT" width:140
		
		on btn_select pressed do
		(
			if selection.count == 1 do
			(
				curO = selection[1]
				if classOf curO == SplineShape or classOf curO == Line do
				(
					subSplCnt = numSplines curO
					if subSplCnt > 1 do
					(
						subSplArr = #()
						for i = 1 to subSplCnt by spn_Nth.value do append subSplArr i
						setSplineSelection curO subSplArr keep:false
					)
				)
			)			
		)
	)
	createdialog rol_selEveryNthSubSpline 
)

Thank a lot for your help)