I would like to create a report where the user would supply the ending period as a parameter and a hidden parameter would automatically be calculated as the thirteenth period prior to the period supplied by the user.

The report will always retrieve data from the current period plus the prior twelve periods.

I have tried using the FormatPeriod function with an offset but I get a response stating the FormatPeriod function is undefined.

I also want to populate 13 variables for each of the periods selected to use in calculations and placing data on the report.

What is the proper syntax for using the FormatPeriod function in Report Designer?