If you are interested in a particular company is it okay to call and ask questions?

YES! In fact, in some industries, they expect it. I'm in radio, and if the station doesn't get a call from an applicant, they assume they don't want the job bad enough, and won't be a good fit for the position due to lack of enthusiasm. So YES build the relationship. Call before you apply, and a week or so after. Be careful not too annoy them by calling every day, but diligence will always pay off!