Hello, thanks for the invite.
Can do it, will use google maps api v3 with some css styling to create the div to show the filtering function.
Will create an admin page where you can add/edit/remove a location (building project), which will be automatically geocoded (you can manually set de coordinates if needed), of course password protected.
Can show you a working example based on a project i have just finished here, both, what user sees and the admin side.
Thanks!
Edited the bid to fit your budget