I have not used that yarn so can't help there, but 10 balls may not be enough for an afghan and cables do use more. You could add more by doing several colors. Panels different colors or large border.
Here are a few patterns, I've bookmarked, that might be worth a look. Most are worked in narrower panels sewn together. so if yarn weight is not same you can do more panels, any length as needed to get size you want.
http://www.gallentine.org/Knitting/boysafghan.html
http://www.gallentine.org/Knitting/C...ceLapRobe.html
http://www.gallentine.org/Knitting/Squareslaprobe.html
http://www.interweaveknits.com/freep...ing_Afghan.pdf
http://people.delphiforums.com/knit_...gle-afghan.htm
register free to download of these
http://www.freepatterns.com/list.html?cat_id=362
http://cache.lionbrand.com/patterns/....html?noImages=