How to work out total headcount per Month using two date columns?

Hi

I have a table called Staff_Starters (Table) which is connected to a Date dimension.

I got the formula which calculates the headcount per month but does it in a calculatable table & but does not include other columns like FullName, position, etc which I would need to create a relationship with my other tables.

Is it possible to add it to my Staff_Starters as a calculated column or measure?

I am not sure if the formula below is calculating correctly as it uses the columns below;

• DateEmployed
• TerminationDate

The formula counts everyone that has a DateEmployed & stops counting going forward when it has a TerminationDate.

NB: My TerminationDate for active staff is now set to 1899/12/31

Total Headcount = 
var MinDate = FIRSTDATE('Staff_Starters'[Date Employed])
var Result =
SUMMARIZE(
    FILTER(
        CROSSJOIN(
            ADDCOLUMNS('Staff_Starters',"End Date",if([TerminationDate]=DATE(1899,12,31),DATE(3000,01,01),[TerminationDate])),
            ADDCOLUMNS(
                CALENDAR(
                    MinDate,
                    TODAY()
                ),
				"Active Month",DATE(YEAR([Date]),MONTH([Date]),1)
            )
		)
            , [Date] >= [Date Employed]
            && [Date] <= [End Date])
        ,[Active Month],
        "Head Count", COUNT(Staff_Starters[StaffID])
        )
return Result