Once they approve it, make sure to remind them a day or two in advance that you won't be there that day because of your R.O. We've had a few people bump heads with FT's and PT's in the past when they'd "forget" about it and receive a phone call demanding why they weren't showing up for work.
Also don't forget to check the SRO to make sure they accurately log that it was an R.O. and not a "no call."