What you are asking for is not possible using traditional methods in Keynote, a loop in Keynote loops all the slides in the presentation, not just a group of slides.
There is a workaround by exporting to a "movie" file the slides you want to loop, not ideal but it does work:
- add slides 5 to 10 in to a new presentation then export to movie; (File > Export > Movie)
- delete slides 5 to 10 in the original presentation
- place the movie on to slide 5 of the original presentation and set it to loop; (select the video on the slide then; Inspector > Format > Movie >
- set the movie to play automatically; (select the movie on the slide, go to Inspector > Animate > Build In then click the Build Order Button, in the Start Dropdown menu, select After Transition
pressing spacebar will advance manually to the next slide which is the contents of the former slide 11