Date update - like [TODAY] command

I need to be able to display a date and warning based on today's date minus 5 days but I cannot use the [TODAY] command in SP 2013.  I was told that you can set up a workflow that allows a refresh in the list.  Can anyone guide me to a "How To" on how to set up the workflow?  I assume this will need to be done in Developer?

thanks in advance!