[Excel] Need help with creating Excel Add-in

I am trying to find example code to help jump-start me in the development of an Excel add-in that will add functions and cell formatting. I am using VS 2010 (VB.net – not VBA) and Excel 2007.

I was able to create a quick Excel Add-in using the VS template (Excel 2007 Add-in). With this template I was able to add code to modify cells on certain events such as application open, Close, Double click, etc… I was also able to add a custom ribbon tab with a few controls, but I could not figure out how to modify cells with the ribbon code (Only simple things such as msgbox). None of this is useful for what I want to do.

I am trying to add a few new functions to Excel with the Add-in and I am trying to do a few simple cell formats with the Ribbon buttons.
Any help would be greatly appreciated.