change multiples div class from another div

I'm trying to change (better would be to add) a class name to multiple divs using an onmouseover function in another element . the two elements are not nested to eachother so i can't (or at least don't) think i can use plain CSS to do so. i'm simplifying the following code to make it easier to read. the actual html for the "items" is a little bit more nested. hope this won't be an issueI'm trying to change (better would be to add) a