So, this should do the trick…
Idea is to add some parametars to URL of your landing page so Google Analytics can differ visits that came from clicks on your banner or link.
You can do that by adding ‘?ref=MyBanner’ at the end of URL of your landing page.
For example, if you want your banner to point to address:

http://www.domain.com/my-product.html

then your tracking link would be:

http://www.domain.com/my-product.html?ref=MyBanner

Then, code for flash banner button (Actionscript 2.0) would be:

on(release) {
getURL(“http://www.domain.com/my-product.html?ref=MyBanner”, “_blank”);
}

You can also add some more parametars to your URL if you want, just seperate them with ‘&’, Example:

http://www.domain.com/my-product.html?ref=MyBanner&site=linkexchange&banner=468×60_blue_banner

After some time login to Google Analytics and go to ‘Content overview’ section, there are listed all your pages that have been visited.
Filter your content with keyword that you added to your link, in this case: ‘ref=MyBanner’, and you will get number of page views that came form clicking on the banner
1 page view = 1 click on banner.

I’v tested this with Google Analytics, but i think it should work with any other tool you use to mesure statistics of your site.

For more advanced way to track online campaigns with Google Analytics visit Google Analytics help center and use URL Builder to generate your tracking links.