Display Custom WPF User Control using Code

Hi to all,

I am working on a WPF application that load Items from my database into a WPF Listview in a Gridview View. I have a Checkbox next to each loaded item. When the checkbox is checked I want to display a custom user control, but for the life of me can't figure out how to do that. The fact that I have been working 2 days straight on this might have to do with it and I would really appreciate any help with this. I can't load the user control for each Item (I think), because there is a minimum of 500 Items. This must be done by code.

Thanks for the help