Re: input field - set input field values using Macros
I don't think that a macro-approach would be useful. Unfortunately I didn't understand what your expression is calculating - you could refer to your input-fields per label/column()/direct expression and also use advanced aggregations with total-qualifier and aggr() functions - but if there are anything else as inputsum() within the expression they wouldn't be editable anymore.
If you need further editable functionalities then you will need to use more inputfields, maybe in another scaling. Inputfields are good for simple use-cases - if it goes to more complex (forecasting) models it will be quite difficult and other solutions might be more suitable: SQL Writeback from QlikView extension object.