Excel formula

For gantt type chart I have a start date - in column I have =TODAY()-F9 the start date.  I want to show days completed - my issue that if todays date is past the end date, it continues to show todays date to the start date.  I want it to show it to show the days completed but no more than the number of days within the range of start to end date?  So for cell K9 I want it reflect 21 days.  Days completed should never exceed work days.  Help!!