\Kenly\ \gave\ me\ an\ answer\ \answer in Stack Overflow about how to do it through the KanbanView.ColumnProgressBar template, in case someone is interested.

Before he aswered, I found another way when analyzing the Column Progressbar js code.

I inherited that js code and expanded the functions to do the same process already made with sum_field, but with another sum_fieldB field. This makes the new field look and feel as if it was already part of Odoo, with the same animation and format as the original sum_field.