Be candid with the interviewer when sharing your level of experience with Excel. Your honest response will help the interviewer prepare a better training plan for you if you're hired for the job. Tell the interviewer if you're a beginner, intermediate, or advanced user of the system. Then share a few projects you created using Excel as well as accounting tasks that you regularly complete in the system.
Don't assume that you don't need Excel knowledge to handle an accounting role. Yes, there are many types of software available but none can currently replace Excel. It's the most widely used and most companies prefer it.