How do you drive net sales for the year you pass in? That is a business requirement, once you find out the requirement, we can build the calculation for the calculation column.
"Net_Sales" * $$ip_year$$ means that Net_sales is a column, ip_year is a input variable, you refer the input variable with $$ as prefix and postfix. Here we are multiplying the year with net_sales column for each record.
Thanks,