Get stock change (old & new) on variable product

I´m facing an issue:

I can´t get the stock qty changes on variable product.

(I mean: the variation ID2500 of product ID2499 changes his stock from 5 to 10. I should get the delta (more 5 units))

I need to know the previous stock and the saved new stock when the client updates the product variation stock.

I´ve tried using pre_post_update, woocommerce_before_save_product_variation hooks, save post, etc and I can´t get the change of stock.

Please your help with it.

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