How can I perform partial reloading within a Tobago Sheet? (Java)

Question

I am using JSF MyFaces 1.1 and Tobago 1.0.27. Now I would like to create a sheet with partial reloading. I know that I need to know the ID of the specific control within my sheet, which has to be reloaded if for example a button is clicked. The problem is, that this ID contains the row number of the current row within the sheet. How can I obtain this number within my jsp code?

If I am right, the button of each row has to have the following attribute:

<tc:attribute value="mainPage:%ID-OF-THE-CONTROL%_data_tr_%ROWNUMBER%" name="renderedPartially" />

I already found out how to get the ID of the control but where do I get the rownumber from at this moment?