I can only suggest to contact your broker and find out if EXE is available to short for starters. If it is, then ask them how to go about it, will they require extra margin even though you have the call option, what are their fees, what is interest for hold short shares.
You will obviously want to ensure that you don't end up paying more fees than any profit you make - and that is entirely possible depending on their fee structure. You will have the fees of shorting and then fees to buy back to close the share position. If you are with a discount broker, it may not be an issues - just pointing out the things for which I would be looking in your situation.
Brokers sometimes handle things differently, so it's important to know from your broker. I have seen people get into all sorts of trouble with lack of knowledge especially with options, so I suggest you contact them in the morning and find out as much as you can!
