Set default application folder for plug in msi based on existing application path

Hi All

I've got an application that uses plug-ins to represent different flavours of sql (e.g. MySQL, PostGres, SQLServer etc.). The intention is that further flavours of SQL will be supported by developing further plug-ins. It uses MEF to discover any dlls in a given directory (called SQLFlavours) which expose a given interface. The SQLFlavours directory is a subdirectory of the main apps application directory and is therefore a relative path.

I've created a deployment project for the main application and there's a default location but the user can change it if they wish. I'm now trying to create a deployment project for one of the plug-ins but I'm stuck on how to set the default location for it. Ideally I'd like the installer to somehow "search" to target PC to find the appllication folder of the main app and then append /SQLFlavours to create the apropriate default location for the plug in. Is there any way to do that?

Suggestions?

Cheers
FD