Creating a "Rank" field


Is there a way to calculate a rank based on the value of a field? For example, if the field is Total Sales, I can sort in descending order by this field, but can I create a formula that gives me the rank of each person in another field?


I am guessing based on zero responses, that this is not possible. I am looking for a similar solution in that I want to rank by grouping e.g. I have 20 people with an overall total for a field entitled CUMM of 1000, with the data set grouped by the PACKAGE field/column.

I am looking to rank by subtotal of the field CUMM for each change in PACKAGE, but cannot find anything currently that will accomplish this.