Change list item's value with frontend value while creating list recursively

Hey y’all!
Hoping someone can help me here!
A list is created recursively when selected but a calculation is made in an RG cell on the front end that I need pushing in to the relevant cell in the new list - any ideas please? I’ve tried allsorts and need a second pair of eyes…

I’m not sure this question makes much sense, but why don’t you just recursively do it in the front end?