iPhone: redirect to app store on mobile safari if app is not installed

I have two links on an optimized mobile Safari web site. One is a link to the App Store to download my application. The other is a Launch App button which uses the registered app:// protocol to open the application. The problem is that mobile Safari chokes when the user clicks the Launch App button if the application is not installed. Is it possible to detect if the registered protocol is available, and if it isn't, change the Launch App button with an appropriate URL, such as the download app URL, so that the user doesn't get a nasty popup?