One important aspect of climbing the career ladder is continuing your training. There are any number of seminars and training classes out there available for administrative support personnel, however some of them are terribly expensive.
If your employer doesn’t pay for continued training for administrative personnel (and I’ve worked for more than a few who don’t), check out your local community college or technical school. These places often have non-credit, continuing education courses at a price far lower than many of the big name providers. Just call and ask if they have a continuing education catalog and ask them to send it to you. Many will have classes specifically on administrative topics as well as various Microsoft Office trainings.