if you need to counteract the sleepiness from benzos, try something with a longer duration than cocaine. using cocaine would mean that you redose multiple times. clonezepam is long acting, cocaine is short. this is a perfect recipe for addiction.
if you have a script for the clonazepam, maybe your doc would consider writing you a stimulant.
as for short term effects, mixing uppers and downers makes it more likely that you will overdose. people on benzos/alcohol/opiates tend to do a lot more coke than normally because they don't feel as much anxiety. your heart will feel it though.
or, i suppose you could end up ODing on the benzos because of the coke masking the effects.
anyway, be careful and keep track of how much you are consuming. if you do it right, i don;t think there are any risks that you don't already know about.