Responding to event in pop-up window

I could have swore I used to see a tutorial on this site that talked about how to create a pop-up window and respond to events from that window.
This is exactly what I want to do, create a window with a gridview - have the user selected a row, and return the selected row back to the calling page.
Does anyone know where this tutorial went, or where I can find a good one?

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