Hi Jorden,
To upgrade users within s2Member, you need to set up Billing Modification Forms from within your dashboard under s2MemberJ -> PayPal® Pro-Forms -> PayPal® Pro Billing Modification Forms. There you can set up forms to upgrade to different Membership Levels, and display different forms based on conditionals within your page. You can check out Dashboard -› s2Member® -› API / Scripting -› Simple/Shortcode Conditionals for information on how to set those up.
s2Member will then update the billing information for the user’s subscription to match the one they just upgraded to.
If I have a “gold” level member @ $200 and they want to upgrade to a Platinum membership which is $450, how does S2member handle this?
To do this, you would put something like this within your page:
[s2If current_user_is(s2member_level_3)]
[s2Member-Pro-PayPal-Form modify="1" level="4" ccaps="" desc="$250 USD / One Time ( for lifetime access, non-recurring, no trial )" ps="paypal" lc="" cc="USD" dg="0" ns="1" custom="mysite.com" ta="0" tp="0" tt="D" ra="250" rp="1" rt="L" rr="BN" rrt="" rra="2" accept="paypal,visa,mastercard,amex,discover,maestro,solo" accept_via_paypal="paypal" coupon="" accept_coupons="0" default_country_code="" captcha="0" /]
[/s2If]
Let me know if you need anything else clarified :)