Certifications are an excellent way to demonstrate proficiency.  Depending on your career, there are numerous certificates that can help make up for lack of experience.  For almost any knowledge worker, proficiency in Microsoft Office products can move you up in the candidate pack, plus having a certificate to back up your claims on experience is definitely more credible.
Check out Microsoft Certified Application Specialist Series

They offer application certifications in all the main Office products and they an excellent way to ensure you completely understand the products and they are fantastic to add to your resume.