Use personal.xls for all sorts of stuff, its built up over about 10 years now
Auditing tools, sheet protection / formatting, incrementing ranges of numbers, deleting ranges that meet specific criteria, applying conditional formatting, applying version control and saving, appending text to equations / ranges of data etc etc
Its easy to update an interface in Excel, by writing new tools into a drop down menu bar, rather than creating icons. This still works in XL07, but not as well as in 03 (its hidden away in the "add-ins" tab)