It's possible with a script, but why would you want a script to add eight guide? Just draw them by hand. If you would like them to appear on all pages, then draw them on a master page.
Are you familiar with master pages?
Alternatively, are there other requirements?
By the way, it would be helpful to use a more descriptive title. I think you may still be able to change by clicking "Edit Thread" on the right. Something like "Adding guides for page borders?" is much more helpful than "New to scripting."
Agreed on the descriptive title. You should also pay attention to properly naming your ID -- I presume you mean CS5, which (annoyingly!) is something else than 5. You have to thank the Adobe marketing team for that ...
As for adding guides, I also agree with John (hi bud!) that it's absolutely not necessary to venture into scripting for that. But I'm going to take a stronger position than that: it's not necessary to add any guide, whatsoever!
Apparently, you need the guides to properly have your photo's bleed off the pages. Well, first off, there is no need to place guides on the page borders themselves, is there? They are already visible, and if you test, you will see they are as magnetic as any hand drawn guide.
Second: as for the 1/8" outside borders, you cannot add guides outside pages. Fortunately, that's not a problem, because if you check your Document Page Setup dialog, you might see a little button called "More"; and if you press that, you will get a host of more options, including for what you were trying to create by hand: bleed.
.. as for the 1/8" outside borders, you cannot add guides outside pages. ..
Uh, of course you can, but what I was aiming for was: you cannot add guides outside master pages. Anything you add outside the page area of a master page will not appear on the pages that you apply it to.
(Unless you want it to -- but then you'd use the Slug area, which happens to be in the same dialog as the Bleed you were lookin' for.)