Aggregate items based upon their sales history

Hi All,

We have requirement to do slice and dice items based upon high-medium-low runner in a worksheet.

Item will be marked as high-Medium-low based upon %age of its actuals versus Total(actuals) for particular product Line.

This calculation happen every month end and update item(either High or Medium or low) based upon the %age value.

End user wants to have this performance category(value: High,Medium and Low) as a level so that he can add it as aggregate parameter in a worksheet.

Is it possible to have it as a additional level where in we know that its value for a particular Item is dynamic(can change every month).