One time fixed fee for whole order

Hi,

I’m using PPOM plugin to add an additional service that a customer can purchase. The service can be applied in any of the products, I have it as a PPOM checkbox field. The thing is I want to charge only once for such a service on the checkout. Means If a customer applies such a service at least once I want to add ONE TIME FIXED FEE to the whole order. For example, even If someone applies a service two or three times (each time in different products) and then proceed to the cart and checkout, would only see one-time
fixed fee of the price of one service (not summing everything up). Is there a way I could achieve that using this plugin? I’ve noticed there is an option of a one-time fee to the cart total, but it sums up everything.

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