How to create a minimum order total in Marketpress

I just upgraded from Marketpress Lite to full Marketpress so that I could set a minimum order.

I can’t seem to find an option for this (I can find an option for the maximum anyone can order of any item, but no minimum).

Ideally what I would like is for any order that totals less than a certain amount to be rejected. I had assumed that this would be built in to Marketpress. I have also tried the code from here, but with no success:

If it’s not possible to set a whole cart total I would at least like to be able to set a minimum order amount per item, I’m assuming that this would be coded in almost exactly the same way as the maximum order amount that is in the plugin.