If it is one bottle every few days, you will be fine. Some women can even do one bottle a day and their supply is ok. But some women can't - they need to pump for that bottle feed to keep their supply up. If you skip the feed, your body *could* think it doesn't need to make as much for the next feeds.
If you do end up pumping, you could always use that first and top of with formula. It takes a while for your body to get used to pumping, so give it a few days. I have used an electric Medela and a hand Isis pump and the electric definately pulls more milk and much faster.