Attached is one method. A table calc called "Min Price jtd" using IF FIRST()==0 THEN WINDOW_MIN(SUM([Price])) calculates the minimum price, with Compute Using set to Supplier but only returns a result for one row in the partition. Then a "Total Min Price jtd" calc using WINDOW_SUM([Min Price jtd]) totals up all the minimum prices. Two more calcs do the same for the Max price.
sum of max and min.twbx.zip 33.8 KB
Thanks Jonathan, it's a perfect solution: