Sum monthly hires and spill by discipline in excel

I have a table called StaffDetailsTbl that has employee data with associated discipline and start date as below:

I'd like to sum the number of hires per month by discipline in a new dataset like below:

The timeframe in K2 (starting from Aug-17) is determined by the following formula where StudioProjectedOperatingMonths is a defined name with the value of 401:

=EDATE(StudioStartDate, SEQUENCE(1,StudioProjectedOperatingMonths,0))

The Disciplines in J3 (starting with Programming) is spilt with the following formula:

=FILTER(DisciplineTbl, {1,0,0,0})

Is there a formula that can be entered in to K3 such that it sums each new employee from the Employment Start Date in the StaffDetailsTbl for the duration of the defined timeline and spills the data for the disciplines in column J?

For example, August 2017 would have 5, December 2019 would be 6 and Jan 2020 would be 8.

StaffDetailsTbl data:

Update

I now have the following formula that will spill the contents for the number of columns:

=LET(StartDateToCompare, K$1#,
YearToUse, YEAR(StartOfMonthToCompare),
MonthToUse, MONTH(StartOfMonthToCompare),
DaysInMonth, DAY(DATE(YearToUse, MonthToUse +1, 1) -1),
EndDateToCompare, DATE(YEAR(K$1#),MONTH(K$1#),DAY(DATE(YEAR(K$1#), MONTH(K$1#) +1, 1) -1)),
EmployeeDateToCompare, StaffDetailsTbl[[Employment Start Date]:[Employment Start Date]],
COUNTIFS(StaffDetailsTbl[[Discipline]:[Discipline]],$J2, EmployeeDateToCompare,">="&StartDateToCompare, EmployeeDateToCompare,"<="&EndDateToCompare)
)

Is there a way to adjust this so it will also spill for the number of rows in the DisciplineTbl so I can just insert the one formula and not have to drag copy it for all the rows?

If I'm understanding your question correctly, consider using "Countifs" which allows you to count the number of items based on multiple criteria. For your scenario, I'm seeing you want it to count the item if:

• The datasheet discipline matches the discipline shown on the report header,
• The datasheet start date is greater than or equal to the report header date (set the dates in the report headers to the first of the month; they can still be formatted to only show month and year), and
• The start date is less than or equal to the end-of-month date of the header date.

I'm not clear on where your J and K columns are as I'm only seeing column headers in the first image, but assuming in the second image, your selected cell is B3, then I would use the formula:

=COUNTIFS(StaffDetailsTbl![discipline column],$A3,StaffDetailsTbl![start date column],">="&B$2,StaffDetailsTbl![start date column],"<="&EOMONTH(B$2,0))