R help - Jan 2006 - rsq.rpart not found ...

Hi to all
I tried  help.search("rsq") and found


Help files with alias or concept or title matching 'rsq.rpart' using
regular expression matching:

rsq.rpart(rpart)        Plots the Approximate R-Square for the
                        Different Splits



then I tried to use the function but I got the error object not found
must I load any package before? there is nothing in the helpfile (R 2.2.0)

Regards Knut

>library(rpart)
Regards Knut