Iterate over multiple checkboxes and get titles of selected

I have an app with a window containing a box that contains maybe 100 checkboxes.

When I press a button I'd like to build a string of the titles of the selected checkboxes.

I know I need to iterate over all the checkboxes and get the titles but I can't figure out how to do that. Any pointers would be greatly appreciated. I know how to do it with bindings and tags but with 100 checkboxes that's just crazy!

Thanks!