you can set up channels in your adsense account to track the ctr, impressions etc of each individual ad unit.
channels are a must for any webmaster with multiple sites... keeps your revenue earnings clean and easy to read...which allows you to make any changes you might need...and is a godsent when trying to sell a site and showing proof of income. Just make sure you follow the TOS with google when showing potential buyers your revenue...google does not like you to show off your CTR ect...so you have to block those items out from the screen shot.
I'm just curious, but why is that you can't show or talk about your CTR? Of what particular good can that do you or anyone?