You can use RunningValue function as the text value of the line number column.
If you want a numbering for rows within a dataset, you can use
=RunningValue(1, SUM, "Employees")
where Employees is the dataset name.
If you have groups in your reports, say one of the groups has a name "EmployeesByCity
", then you can replace the last part of the RunningValue with this group name shown as below
=RunningValue(1, SUM, "EmployeesByCity")
You can check the below link for a samplehttp://www.kodyaz.com/article.aspx?ArticleID=40