Right now i am using this custom value: '{{payment.total_amount}}' as LeadValue in the 'Create Or Update Opportunity' action in workflows that triggers when a new payment is registred to dynamically give my leads the Lead Value that matches the total amount of their payment.

But it would be nice with a custom value that represents the total amount that a client has ever spent in their lifetime.

So for example when they subscribe on a subscription and they pay the second rate. I would like a custom values that now represents the total amount of both the first rate and the second rate.