Undo on any rollout UI or variable

try(destroyDialog Combobox_rollout)catch()
 
rollout Combobox_rollout "ComboBox"
(
	button btn_1 "Add"  across:3
	button btn_2 "Remove " 
	button btn_3 "Box" 
	combobox cbb items:#("line 1") height:9
	spinner sp "spinner"
	------------------------------------------------------------------------------------------------------------------------
	fn AddLine cbb = (
		temp = cbb.items
		append temp "new line" 
		cbb.items = temp
	)
 
	fn DeleteLine cbb = (
		if cbb.selection > 1  do (
			temp = cbb.items
			deleteItem temp cbb.selection
			cbb.items = temp
		)
	)
	------------------------------------------------------------------------------------------------------------------------
	on Combobox_rollout open do ( 
		clearlistener()
	)
 
	on cbb entered i do with undo on (
		if i != "" and i != undefined then (
			cbb.selected = i
		)
	)
 
	on btn_1 pressed do (
		undo on (
			AddLine cbb
		)
	)
 
	on btn_2 pressed do (
		DeleteLine cbb
	)
 
	on btn_3 pressed do (
		undo on (
			box()
		)
	)
 
	on sp changed i do with undo on (
		print "TEST"
	)
)
createDialog Combobox_rollout