Dax Formula

Hi, 

According to your description, I can roughly understand your requirement, I think you can try to use this method to achieve your requirement:

This is the test data I created based on your description:

First you can create a calendar table to place into the date slicer as the selected date, you can change the date range based on your dataset:

Calendar = CALENDAR(DATE(2021,1,1),DATE(2021,1,5))

Then you can create a measure like this:

Count of diff =

var _selecteddate=SELECTEDVALUE('Calendar'[Date])

var _CountofStart=COUNTX(FILTER(ALL('Table'),[StartDate]=_selecteddate),'Table'[StaffNameStringId])

var _CountofEnd=COUNTX(FILTER(ALL('Table'),[EndDate]=_selecteddate),'Table'[StaffNameStringId])

return

_CountofStart-_CountofEnd

And you can create a date slicer and a card chart to get what you want, like this:

You can download my test pbix file below

If this result is not what you want, you can post some sample data(without sensitive data) and your expected result.

How to Get Your Question Answered Quickly 

Thank you very much!

Best Regards,

Community Support Team _Robert Qin

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