Thematic map: the size in points is proportional to the square root of the data value

[anhvivian]

I have read the link http://forums.esri.com/Thread.asp?c=93&...30&t=213906
I found that the size in points is proportional to the square root of the data value
Pj = (Valj/ValMin)^0.5 * Pmin

In case, i want to replace the square root by another function. Ex: log10, cube root...
Using ArcObject can do this?

many thanks! (I need a help in hurry)