Adding my own function category in Excel

I have created my own Excel add-in, Analytic.xla. When I add it in to Excel 7 via Tools..Add-in, functions contained within the add-in are added to the User Defined function category when viewed through function wizard. Is there a way of creating my own function category under which those functions within the add-in would appear, rather than always appearing under User Defined category? For example, if I had function called MySum within the add-in, when function wizard is run it would show all usual function categories (Mathematical, Statistical, etc.), my own category (say, e.g. MyCategory), AND User Defined category. The MySum function could then be found, of course, only under MyCategory category.