I need to insert a tracking code in the woo URL to know new customer or old

Hello.

I’m affiliate wit some companies which give cashback to customers when place an order in our website.

At moment we give 8% of cashback. But we need to change this for 8% new customer and 4% for customers which already purchased in the page.

They told the following to me:

“It would be best to pass us via your tracking whether it’s a new or existing customer, so we can assign the lower commission to existing customer orders automatically, rather than you amending pending sales for existing customers each time.

There is no way to pass us this if you are using our WooCommerce module at the current time, so if you wanted to do this you would have to add your tracking manually to your website and add ‘&newcustomer=X’ to the end of both URLs in the tracking code where X is either Yes or No depending if they are or are not a new customer.”

Any idea on how can I do this with Woocommerce?

Thanks