pricing according to scales

i have created a new condition type and i want to maintain the record in such a way that every pound(LB),the price is increasing and it is not a steady amount which is increasing.Some times it is increasing in some cents or dollars.After 100 lbs the price is increasing like $1 to every pound.I am getting very confused.Thanks in advance.Please throw some light on the how to maintian Condition type and the condition record as well

Thanks

Raj