Is it possible to purchase PPV with Cox On Demand?

I was very happy to see Cox On Demand arrive shortly before the Floyd Mayweather fight. I figured I'd be able to purchase the PPV. But the day of the fight I couldn't find anyplace in my Roamio Pro's Cox On Demand menu to do so. As a result I had to go get a Cox box for the day which was a huge inconvenience.

Is there another way to accomplish this or is it simply impossible?