Employee Tenure using Power Query or DAX

[DAXEupheme]

I am needing help with the following.

* Ideally done via Power Query M, but DAX measure would work as well.

* I have a separate dimDATES table, and it is a normal 'calendar' table, not 4-4-5, etc. -- so the built in TimeIntelligence functions can be used.

ISSUE - my FACT table contains employees who appear in the report for each month every time they take a call, which means they can appear multiple times each month.  I'm using a PivotTable with Months and EmployeeName to show (by number) the unique times they are appearing each month, as a running total.

For example, if John Smith takes a call in NOV 2018 (and it was their 1st month taking a call) then the TENURE column in the PivotTable will show '1'.  If they take a call again the next month, then it will show '2', etc, and it will show a '3' if they are take a call in JAN 2019, etc etc.  So a running total.  All of my measures thus far are counting the total number of times they take calls each month and adding them up, which is not what I want.

Ideally, I would like this to be done in POWER QUERY using M -- create a new column TENURE that recognizes the first month an Agent takes a call (thus their first month of employment) and then recognize if they take a call during the next month, the tenure for that month becomes '2', etc. etc.

Much thanks!

Here are the DATE COLUMN names I have thus far in my QUERY -

[Anonymous]

any chance you can upload some sample data from your fact table?