Debra Dalgleish has instructions with pictures:
http://contextures.com/xlfaqMac.html#NoMacros

George D wrote:

I had several macros in an Excel workbook and have deleted them, but I still
keep getting the Macro security warning when I open the workbook. This
woekbook does not open automatically when I start Excel. If anyone can give
me some advice or how to go about solving this problem it would be much
appreciated.

--

Dave Peterson