Sum of Range based on numbers in a different row

Hi, I would appreciate any help I can receive on this spreadsheet, which is being used for tracking employee absence.  I am trying to sum the total of a range.(the sum of the hours taken in the month).  This is for an employee who is working a flexible schedule and is not working the same amount of hours each day.  The issue is if the employee is off for the full day there is an X in the field.  That X is represented by a value in the row directly above it; each day in the month is given a value.  If the employee is off for only a partial work day, the number of hours is entered into the field instead of the X.  I have attached a sample of the spreadsheet, which should help better explain what I am trying to accomplish.  Thank you.