Code for "Balance Checker" for gift cards

Site URL: https://www.gobackyouforgottheflowers.com/onlinestore

Customer Support suggested I contact this forum re: my inquiry--How do I set up an option for customers to check the balance on their e-gift cards? I have a Commerce plan with Squarespace.

Right now I use my own internal bookkeeping software to send customers statements of their e-gift card balances; I'm searching for another method that eliminates having to do this work twice. I do know that Squarespace automatically calculates the balance of a gift card for a one-time purchase, but I'm looking for an option for multiple purchases on the same gift card over a period of time (i. e., customers would insert their electronic code from their gift card into a "Balance Checker"--check screenshot below--to get an updated balance on their e-gift cards). Customer Support suggested that I may be able to insert some code to accomplish the goal of having customers inquire the balance on their e-gift cards over a period of time. 

In my case, customers may purchase a $500 gift card for example, then use that toward purchases in my on-line store. However, they may purchase something on a weekly or monthly basis, carrying the gift card balance over to the next transaction a month into the future. 

I've attached a screenshot of another Web site of what I'd like to accomplish; that Web site is supported by Squareup. Customer Support informed me that Squareup and Squarespace are two separate entities. 

Customer Support also said that Squarespace has no plug-in or third party app that would support my concept of a "Balance Checker". What suggestions does anyone have? 

Thank you.