Wondering how to handle a situation with respect to IP and banners, etc... We recently started selling large format banners (Flash) on our site for clients. We design/produce the banner and place it on our site(s).

An advantage we have over our competition is that their banners are dull and non-Flash-y But now our clients are asking for the banners we made for them to be placed on these other sites. This of course removes one of our advantages - and we end up doing all the work(!). Ideally, we would not want the ads we produce to be displayed on our competitor's sites.

Additional background:
* Currently, we were not charging for creation of the ad, but were thinking of charging an hourly fee for creation (usually 1-2 hrs. +) - can we still charge for the ad but say it can only be used on our website? (And is this type of thing done commonly?)

* We were also thinking of keeping the free production, but if asked for the ad to place on other sites, charge some kind of "transfer/release fee" to cover the cost of production (and then some - like several hundred bucks). Though at first blush, this seems to punish the clients more than our competitors.

Was wondering if others have faced this dilemma and how have they handled it?