Page Layout Extent

We are trying to create a spacial index of the page layout of each of our map projects. We want to be able to create a map project, save it and run a script to "capture" the spatial extent of the page layout so we can later query the map by clicking on a point and having a result of all of the map projects that were associated in the area.

Any ideas on how to do this programatically or with a model? We don't want to reinvent the wheel if it has already been invented.