Workflow to alert users if they haven't logged a specific type of activity within the last 7 days

[CRMsimple]

I just got a request to have an email alert sent to any sales users who haven't logged a specific type of activity in the last 7 days. It is a requirement (a loose one) that each sales rep must set up one client meeting a week that involves bringing a member of executive mgt. to the meeting. I currently have a dashboard that goes out weekly that shows a list of users who have and have not setup one of these meetings. (You'd think mgt would know if they've gone to one of these or not)

I am also exploring  workflow and email alerts but I'm wondering if anyone has tried this - not sure if you can even set up filter criteria to achieve this.

Any thoughts and ideas will be appreciated.