Word 2010, How to Page Number 1a, 2a, 3a, etc. HELP!?

[aabx]

Want to start appendix 1a, and have the rest of the section 2a, 3a, goes on for 20 pages. I have a previous section numbered 1-25 which I don't want changed.

I tried creating a new section (Page Layout,Breaks, Next) and disabled 'Link to Previous" and started the new section at page 1 and manually inserting the "a" but it effected the previous section 1-25. I also right clicked on the page number and played around with Edit , Fields and Chapters, but could not figure it out, especially so the first section wasn't changed.

I appreciate any detailed (simple as possible please for us simpletons) explanation.
Thanks so much!
Specs: I have Word 2010,Windows 7, HP Pavillion purchased April, 2011