I am using Office 2003 on Windows XP.

I just want to add a single custom control as the first choice on Excel's
built-in right-click shortcut spreadsheet menu ("Cell").

I want all the functions to work as normal, but I only want it to work in
the current file. Since changing the menu affects all files, I think the menu
needs to be rebuilt with my custom control (a button) at the top.

Can anyone offer any suggestions on how to do this? Please post example code.