Hi Ramesh,
There are many ways to do this in CR however, almost all of them are the most inefficient ways to arrive at.
The best solution, as Raghav stated is to create a look-up table that holds all the Fridays and Friday-1 is it's a holiday. This way, you can make sure everything is passed back to the database for processing.
Another way to do this, if you cannot create a look-up table is by adding the logic in a PL/SQL block and using a Stored Proc as the datasource for the report.
-Abhilash