Criteria Design

Hello,
One of out clients has changed criteria of entering data in to a application that I designed about a year ago. Initially based on particular value of a field they have to meet certain set of requirements and select the same number of requirements from a give list provided to them through a list box.

No, the client want to modify the requirement selection to a preset based on the value of the field. For example:
if the value of the filed is 20 they have to meet about three requirements and out off the 26 available requirements labeled A-Z. They need to pick from K or J requirement say the meet requirement K three time or J three time or any combination that would result in three.

One good thing about this is that the value of the field goes up say currently it is 60 they need to meet 12 and the criteria is ( 4* (K or J) and 8 * (G or T or N or P)) totaling it 12. It should be noted that they need a minimum of 4 from K or J and 8 from the other list summing the total to 12.

I am wondering what would be the best user interface lay out that I could use and is there as simplest way for me to make this work with out having to hard code these criteria in the Code..

Thanks for you valuable time

Nepotist