Where I can change the array of breadcumb links ($breadcrumb) given to theme_breadcrumb($breadcrumb) in template.php?

Hi,

maybe someone can help me with this question: I want to add Microdata formats to my breadcrumb. So far I changed the themable output with theme_breadcrumb($breadcrumb) in order to give the wtrapping div container a special attribute. But I would need to do this as well for each breadcrumb link / item in the $breadcrumb-array so that each link gets some attribute. Does someone know where I can change the content of $breadcrumb-array?

Best,
Tobias