Unfortunatly, you don't become a Subject Matter Expert (SME) by just taking certification tests. A SME usually has years of direct experience under their belt and without that past work experience, certifications may actually look suspicious. Many professional certification tests (PMP, CBAP) require you to qualify prior to taking that test.

"Individuals interested in pursuing the position of subject matter expert must have a minimum of ten years of directly related work experience in their area of expertise."

http://www.ehow.com/about_6549153_subject-matter-expert-job-description.html

You may look into some of these:

http://www.banktrainingcenter.com/certifications_designations.asp

http://www.aba.com/Training/aib_dip.htm

http://www.ehow.com/list_6567721_certification-courses-banking.html