Code in xlsx workbook?

[rb44]

I have received a macro free workbook from a client (.xlsx). However, when I open this up it does things like checking for a license and creating a menu in the "add-ins" ribbon. When you click on the menu it opens up and add things to the document actions tab. How is all this possible as the workbook has no code? Also, how do I see what else the spreadsheet is doing in the background?

Thanks in advance

[Andy Pope]

It's possible to attached a toolbar to the workbook which will populate the add-ins tab without any code.

What level of macro security do you have set?
Is the file in a trusted location?

[royUK]

Is that the only file that was delivered? Can you attach a copy?