Increase or Decrease font size - http://www.zeigen.com/shortcuts/2007/06/28/font-size/

Divide in Excel - http://spreadsheets.about.com/od/tipsandfaqs/qt/divide_excel.htm

Default to paste unformatted - http://office.microsoft.com/en-us/help/HA010429611033.aspx

Reference of MS office file type and format - http://www.microsoft.com/interop/docs/OfficeBinaryFormats.mspx

Background of why MS office are so complicate to work with, with some solutions
1) Call office as external service , few details mentioned in the articles
2) Use other format that office support 

http://www.joelonsoftware.com/items/2008/02/19.html