how to auto change monthly billing amount?

Hello expert,
What should I do to make s2member change the monthly billing amount? I want to change my client a monthly membership fee based on this formula: this monthly billing = unit license price * Number of the licenses the client bought in this month.
Should I use short code? which parameter should I update? or hooks, which hook should I use?

Thank you very much

Hi Lan,

You will need to create the HTML form necessary to select the license and quantity, then submit that information to another page that calculates the total amount with PHP and uses the dynamic shortcode attribute feature to configure the monthly amount on the purchase button.

Please see this thread from the old forum that explains how to use dynamic shortcode attributes to dynamically set the price: http://www.primothemes.com/forums/viewtopic.php?f=36&t=1604