Financial toolbox/Credit risk utilities/Transprob function/E​xposuretra​nsitions

Is there a possibility in MATLAB to "adapt" transprob function (or if there is another solution) so that it is the percentage of exposure transiting from one rating to another that is the output, and not the number of obligors (in particular time).

Some finance institutions (I guess minority) employ this approach. There can be a large number of defaults from one rating category, but in terms of exposure percentage it may not be that significant (or the other way). How can it be done in MATLAB? Aleksandar