Dynamic Text Field

Content

How do you add a dynamic text field to a report such as Record Count.  I created a text field in the footer and used the following text 'Record Count: {NumberOfRecords}'.  My thoughts were the token would automatically be replaced with the number of records in the data set.

When the report is executed 'Record Count: {NumberOfRecords}' prints as a text field without the token being replaced.  So, how do I define a text field as dynamic?

 

Thanks