Value Field add event in pivot table

Background
When the Pivot table seems to have a custom NumberFormat, the created fields will not carry it. OffTopic: I guess it is normal, sometimes it displays 2, 3 or 5 digits among the same dataset, this is for convience for the user (thus making each cell in the column likely to have a number format different from each), I am not really able to change it, there is another ruling that basically formats cell by cell on the source data (I know it's not ideal, but it is what is convinent for the user and avoids overflooding the workbook with conditional formattings).
I would like to keep that number formatting on the value field when the user adds it to the PT by dragging that field to the Value field.
Problem
I have not found the right event to detect when the field is being added to the Pivot Table, I have tried all the events related to PivotTables in the worksheet, but even by reading to their inputs, I can see that such event may not exist.
Question
Is there an event that detects the field adding?
Further thoughts
I am not quite sure if it exists, my alternative would be to create a button where the user would get the format from the original source by clicking it by using the same code that I use to format cell by cell, but I would like to this be ran automatically when the Value add happens.