[Closed] visibility script

Hey Guys,

I am working on a simple script to set the visibility for an object on and off. It seems to work OK, except that it sets a key on wherever the current time slider is at a value of -1. Does anyone know how to have it not set these extra keys? Thank You.

Code:

			if ((Visible != undefined) and (Visible.isdisplayed)) do
			(destroyDialog Visible) 

(

rollout Visible "Visibility" --create the rollout
(
		group "Set Frames"
		(
		spinner spn_Start "Disappear Frame" type: #integer range:[0,1000000,0] width:100 align: #left 
		spinner spn_End "Appear Frame" type: #integer range:[0,1000000,1] width:100 align: #left
	
		button but_setvisible "Set Visibility" width:100
		)

	on but_setvisible pressed do with animate on
		undo on
		
	(	
		$.visibility = bezier_float()
		t = spn_Start.value
		y = spn_End.value
		
		at time t  $.visibility.controller.value = 0
		at time y  $.visibility.controller.value = 1
	)
		
)

)
–create the rollout
createDialog Visible 175 100