Add Inset Border to thumbnails

I need to add a inset border to the ACTIVE thumb, the thumbs cannot have borders, only the active one, this script is "pikachoose" a jquery script I am using, and I need the ability to still click the thumbs to choose, so no quick hacks, it should look the picture and also function properly, so whatever "active" thumb, must have the white inset border see image for reference