Distinguish aggregated values.

Hi.

Suppose I'm using some aggregation function which gives me several values instead of one. I have seriesClick event handler

with something like following:

And when I click on aggregated value it returns some value from datasource and I don't know why it returns this value. 

Is there any way to distinguish aggregated values from usual (from datasoure) values? Or is there any way to specify returned value in case of my aggregation function?

Thanks in advance.