With paypal add parameter to not apply tax

Hi,

1) PayPlan with PayPal not work correctly when PayPal apply tax, transaction stays in hold
2) because that, I setted Apps in PayPlan to add tax (for the moment for Canada only), the calcul work well except
3) PayPal continu to apply tax. So How indicate to paypal not apply tax (or indicate to used PayPlan tax amout).
Note : I would like to keep seting in paypal for tax for direct billing in paypal.

thanks