I found one earlier, but haven't implemented it yet. Essentially it talked about creating a function which returns rand() or now() and then using that output as a function input to the ImportJSON call. Then the trick is just triggering that function. Ideally a little "Refresh" button would do the trick, but I'm not sure if Google sheets supports anything like that.

Also, check the updates I added today. You can now see your wallet balances. :)