PRE-PAID PLANS POP UP

Hi forum
I’m a Massage Therapist and I’ve created some bundled offers for my clients under “pre-paid plans”.
Now, once a client has purchased a 5-for-3 plan, I need a function that keeps track of the clients usage of the offer.
It could be a pop-up, the greets the client/member once they have logged in with a
“Hi X, you have 3 treatments left on your pre-paid plan. Would you like to book now”

How do I impliment that?

Then you have to store the number of times that they have in total somewhere, like in a data collection together with their user.id and then look up in that table for the information. make a field purchased and one used and then each time they use add in used and compare the two when they logged in

I had hoped there was an app/function/code that would do that automatic.
I’m already doing the “analog” way now, in a simple Notes document, where I keep track of it. But it’s a bit tiresome.