Okay thanks for that solution.. However, I have two main concern.
1. I have some concern regarding to redirection after payment in front-end. Basically, after the user paid via PAYPAL, the user is being redirected back to the website with only blank page?? I can't see where to find the settings about customization of redirecting stuff..
2. In Hikashop > Vendor, I was trying to "PAY" the vendor's commissions fee, after I click PAY, I can see the product's vendor's fee and I was ready to pay, I was redirected to paypal and tried to cancel the transaction and refresh again the page to try again, but the Commission fee in the list is gone.
Hope to hear anything from you.