How to take a percentage of a Credit Card transaction?

Essentially what I am trying to do is setup a work flow similar to 开发者_Go百科PayPal. I have created an application that allows my clients to accept online donations and what I want to do is take % percent of that transaction off the top. The problems I have run into are:

• Authroize does not allow me to take on an additional fee that is paid out to my account
• I could run a report every month on all my clients transactions to determine what they owe but this is less than ideal
• All of the companies I looked at do not allow for aggregation where by all of the donation systems pay into my account then I remit payment to my clients

Does anyone know of a company that allows for this or is my only option here going to be to setup my own Payment Gateway or is there a simpler solution?

Look into Paypal Adaptive Payments. It allows for payments to be sent to two parties. This means you can take your cut and sent the rest to the other recipient.