580EX II how to use the AF-Assist beam without flash going off

Anyone know how to use just the AF-Assist beam on the 580EXII without the flash going off? I

To disable the flash:
Select the third Settings Menu (the yellow spanner icon with three yellow dots)
Select "External Speedlite control"
Select "Flash function settings"
Select "Flash Firing"
Select "Disable"


To enable the AF-Assist beam:
Select "External Speedlite control" as above
Select "Flash C.Fn settings"
Select "C.Fn 8 AF-assist beam firing"
Select "0:Enabled"

Thanks!