Files not found

I have a little puzzle I need to solve. I want to look in a directory
and take action if no files less than 5 minutes old are found. If I were
looking for files which are younger than five minutes, I could just do

find ./ -cmin -5 -exec do-something '{}' \;

Similarly, if I wanted it to take action if it finds files older than 5
minutes I could do

find ./ -cmin +5 -exec do-something '{}' \;

What I need, however, is to take action if there are no files less than
5 minutes old, regardless of whether there are files more than 5 minutes old
or not.


.