Recurring Payments with Authorize.net

[AngelaACS]

I have a client who has used Virtuemart and Authorize.net for years, and now they would like to add recurring donations/payments to their existing store.

They've set up recurring with Authorize.net account, and now they just need it implemented with their Joomla 2.5/VM store.

I've searched the VM forums and found many asking about this function, but haven't found a solution at all.

Hoping someone can assist me and let me know if there is an extension to purchase that works with the existing store, or how I go about setting up this recurring donation/payment feature for their J! 2.5 site?
Thanks in advance for any information to lead me to the solution!