wordpress plugin modification

Hi

I need to add edit a woocomerce stock plugin so it does the following

Sets all item stock to zero except for 2 product ids
then get the amount of items sold in orders with the status proccesing
and remove that from the CSV stock sheet that is being up loaded.
then update stock

for example

Import csv says red hat 10 in stock
2 are sold in orders proccesing
so stock should be 8