Need to be able to change CMS info inside the page's custom code

Just like the title says, I need to be able to change some info inside the CMS using custom code. For example, I have a member’s CMS collection and I want to make it so that when a member joins my membership. They will get 1 credit session available to them once a month. Now what I need to do is use a switch so if it’s on (Using zapier) then they will get 1 credit for every 30 days. Currently don’t know the method of keeping track a 30 day cycle for each page and being able to change a specific CMS page using custom code. So a help of writing a jquery or javascript for this solution will help.

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