how code the Authorise.net reaccuring process...

[eluser]Unknown[/eluser]
Hi,
we purchase a jamit job package in which we used a Authorize.Net gateway to make payment

we need to make a recurring payment with this one...
let we know is there any option to set recurring payment

otherwise can you help me to do... if possible some sample code or related forum link

it is really urgent please...

thanks in advance