Hi,
you can user condition PR02 (graduated scale).
Let´s image that from 151 to 200 price is $100 and from 200 to 250 price is $75
maintain prices as
from 1 to 150 ........price $97.91
from 151 to 200 ... price $150 ..... here $100 plus additional surcharge (*)
from 201 to 250 .... price $75
Your customer orders 180 price is calculated as follows:
PR02 first 150 $97.91
PR02 to 180 $150
total $294.91
if you want surchage in an additional condition, maintain price as $100 and create an additional condition with a conditional formula (quantity > 150)
Regards,
JM