Component Interface Collection Grid Sorting Capability during run time

Hi, We have requirement to use CI in order to use post refund process into Student Financial.

Before we process Refund POST CI, we need change the collection (Grid) amount .For the same we would want to sort the credits in the grid by amount and then start deducting the refund amount from the largest credit down to the lowest credit. That way we will pay charges with the largest amounts first. Is it possible? I saw the peoplebook and found that CI collections has  only three methods to use First(), Item() and Next(). Is there any way , we can achieve sorting capabilities into collection grid? How?