Complex calculations

Hi 
I need to do a custom calculation
there are 3 levels of header 

1. category census & rest of the staff 
2. shift end 
3. staff vs required  

custom calculation formula => (all midnight total x 24)/ all midnight census
how can I achieve this ?
also for census category we don't need 3rd level of header mentioned above, how can we remove that from the table?
Please find the sample data below,

{
"Facility": "ABCD",
"UnitType": "Unit a",
"Unit": "5NH",
"Month": 8,
"DayOfMonth": 14,
"ShiftEnd": "7am",
"StaffRequired": 3.0,
"StaffFirstName": "Tom",
"StaffLastInitial": "A",
"EncounterKey": null,
"RoomBedKey": null,
"PatientInitial": null,
"Category": "R Staffed"
},
{
"Facility": "ABCD",
"UnitType": "Unit b",
"Unit": "3NS",
"Month": 8,
"DayOfMonth": 14,
"ShiftEnd": "7am",
"StaffRequired": null,
"StaffFirstName": null,
"StaffLastInitial": null,
"EncounterKey": "****",
"RoomBedKey": "***",
"PatientInitial": "VC",
"Category": "Census"
},