Sublist label

I’ve created a custom transaction based on the purchase type. By default it has both items and expenses sublists. The labels on those sublists show the dollar value for each list. I’ve also added some additional sublists, and added a similar dollar value display on each. However, I can’t figure out how to modify that sublist label based on changes in the fields. I can access the label property when I create the sublist, but I can’t figure out how to modify it when the fields change. I assume this needs to be done from a client script, but the label property is not available.