Try clicking the Microsoft Office button at the top left of the Excel page.
Then at the bottom right there is a "Excel options" button.
After that there is a list on the left. Try "Trust Center" and see if what you are looking for is there.
Also, if you are used to 2003 version, here is a neat instruction on how to go find a feature in 2007 from 2003....
http://office.microsoft.com/assistance/asstvid.aspx?assetid=XT1014932 91033&vwidth=1044&vheight=788& type=flash&CTT=11&Origin=HA101 491511033&app=EXCEL&ver=12