Hide / unhide balls in time

I have solved it with

for o in geometry do
(o.visibility = bezier_float()
with animate on
(
at time 0 o.visibility.controller.value = 0
at time 100 o.visibility.controller.value = 1
)
)

I started on making a script to do this once upon a time ;o)
It's not finnished, but here it is anyway:

try(destroyDialog roll_VisibilityDialog) catch()
		-----------------------------------------------------------------------------
		-- Function (with animate on)
		----------------------------------------------------------------------------- 
	(
		fn fn_AddVisKey Obj Val =
		(
			VisTrack = obj.visibility.controller
			with animate on
			(
				newKey = addNewKey VisTrack currentTime #select
				newKey.value = Val
			)
		)
		
		rollout roll_VisibilityDialog "Vissibility On/Off V1.0"
		(
			-----------------------------------------------------------------------------
			-- UI STUFF
			----------------------------------------------------------------------------- 
			group "Object Visibility:"
				(
					button btn_VisOn "..:: ON ::.." width:85 height:30 align:#left across:2
					button btn_VisOff "..:: OFF ::.." width:85 height:30 align:#right
					button btn_DelVisKey "Delete Keys On Selected Objects" width:175 height:40 align:#center
					
					slider sld_VisSlide "Visibility" width:175 height:30 range:[0,1,0]
				)
			-----------------------------------------------------------------------------
			-- Visibility Slider 
			----------------------------------------------------------------------------- 
			on sld_VisSlide changed val do
			(
				for obj in selection do 
					(
						if obj[1].controller == undefined do obj.visibility = bezier_float()
						obj[1].controller.value = val
						
						--registerRedrawViewsCallback "Lage en Function" (sld_VisSlide)
						--RedrawViews() 
					)
			)
			-----------------------------------------------------------------------------
			-- Visibility OFF
			----------------------------------------------------------------------------- 
			on btn_VisOff pressed do
			(
				if selection.count >= 1 then
				(
					undo on
					(
						for obj in selection do
						(
							if classOf obj[1].track != bezier_float do obj.visibility = bezier_float()
							fn_AddVisKey obj 0.0
						)
					)
				)
			) -- End on btn_VisOff
			
			-----------------------------------------------------------------------------
			-- Visibility ON
			----------------------------------------------------------------------------- 
			
			on btn_VisOn pressed do
			(
				if selection.count >= 1 then
				(
					undo on
					(
						for obj in selection do
						(
							if classOf obj[1].track != bezier_float do obj.visibility = bezier_float()
							fn_AddVisKey obj 1.0
						)
					)
				)
			) -- End on btn_VisOn
			
			-----------------------------------------------------------------------------
			-- Delete Visibility Key On Selected Object
			----------------------------------------------------------------------------- 
			on btn_DelVisKey pressed do 
			(	
				for i in selection do 
				(		
					deletekeys i.visibility.controller
				)
			) --  End on btn_DelVisKey
			
		) -- End Rollout
		
		createDialog roll_VisibilityDialog 200 180
		
	) -- End Script

The hide property can not be animated by default, because it has no animation track yet. You can add one manually in the graph editor, or use this wonderful script by lonerobot to animate the visibility:
http://www.scriptspot.com/3ds-max/scripts/visibility-assistant
Cheers

Thx, I am looking for something simple with animate on that I can add to may program. I tryed this
for o in geometry do
(o.visibility = bezier_float()
with animate on
(
at time 0 o.visibility.controller.value = [0,0,0]
at time 100 o.visibility.controller.value = [0,1,1]
)
)
but I get

-- Error occurred in o loop; filename: C:\Users\Avner Dei\Documents\3dsMax\Scripts\viz.ms; position: 138; line: 6
-- Frame:
-- o: $Box001
-- Unable to convert: [0,0,0] to type: Float