Updating Prices & Billing Modification

Hello,

I am wondering what to do if I change the cost of subscriptions and also wish to force current subscribers to pay the new subscription cost if they wish to retain their subscriber status past their current term?

I’ve read this post: http://www.s2member.com/forums/topic/if-i-change-my-monthly-fee-question/
As well as this post: http://www.s2member.com/forums/topic/price-change/

But they both are asking whether or not subscribers will not have their subscription amounts changed, so they don’t really apply here. I have not found a question yet asking specifically on what to do if I want to force current subscribers to update.

My current idea is to somehow determine the current user’s subscriber price as well as their s2Member level, and compare that with my new price for the subscripion within a wp_login callback. If they don’t match the new price for the user’s level, set the EOT for the user to the end of the current term and then offer a page with a billing modification form that will (hopefully) unset the EOT and update the subscription amount for the user when/if it is submitted.

The TA and RA amounts / lengths would also have to be calculated dynamically, depending on the time frame within the current user’s term (e.g. 10$ monthly subscription going up to 15$, user logs in 10 days into term or ~33% through, TA charge would be 0.33 * 5$ (difference in cost) for 20 days (remaining length in current term) and regular amount would be $15, which would be charged the next time their subscription comes due).

Getting the current user’s level is no problem, but I cannot find any documentation relating to getting the user’s subscription amount ($) or somehow configuring a ‘base’ subscription amount for each level (that it seems just depends on the form you use, and as alluded to in many other topics I can sell each level of access for different amounts on different pages all by configuring the shortcode differently).

Is there an easier way to handle forcing current subscribers to update their subscription amount to a different price the next time they logon? Thanks!