Count on a column where some value where there are 2 column groups report

Hi i am facing a problem in my SSRS Report where there are two column groupings on the report. Ex: parent group is Location_Head,  chiled group is Location. i need to find out the Count of Employees attendence where it was marked as "WO" (Week off).

Columns in my report are like following

Location Head, Location, Attendace, Week Off (here i need to find out the count of employees where  there attendece was marked as WO)

Please provied me a expression to find out the count off employees who's attendence been marked as WO.

example data

Location Head(Group)        Location(Group)        Total Attendance(total num of empls working in the location under the Loc_Head)         WeekOff

Jack                                     USA                             9                                                                                                                      9 (0n_sundays)      

Jim                                        UK                               10                                                                                                                    10   "

i have a data parameeters too on this report...

so on week days week offs will disply 0 and on week ends is displays total attendance

Thanks & Regards $@m