How to get a report result in a field in custom doctype?

Hi community i have created a custom doctype for day end cash closing. By now i have to run a report for all day sales activity which sums all sales and with that value do the calculations in my custom doctype. I would like to speed up this by adding a custom field that automatically onload do the same sum of sales invoices filtered by the date in the custom doctype. Any help on how to approach this?

Can you have a mockup of what you are trying to achieve? perhaps a sketch :slight_smile: