Custom message for No Search Results

Hi,

I have what appears to be a fairly unique problem. I am putting together a site for a client which uses posts to display their products. They want to be able to create a custom message so that if a user searches for something and there are no results returned, this custom message is displayed which tells the user to call them to discuss it.

I’m having trouble trying to find out how to be do this. Does anyone have any ideas?