The basic idea would be to use OpenReport in your AutoExec macro, with an
expression such as this in the Condition column of the macro:
WeekDay(Date()) = 6
But, there is more to your question that meets the eye.
Firstly, anything you set up in Access will not happen unless the database
is open. Even if you set up a task in Windows to open the database every
Friday, there is no guarantee that the computer will be switched on to run
the task.
Next issue is that if you close the database and open it again on the same
Friday, the report will run again. You therefore need to create a table
where you log the fact that the report ran for this date. The code that runs
the report should then check the table to see if the report has run for the
most recent Friday, execute it if it has not, and write the record to the
table so it does not run again.