MTD Total Column with Multiple Records per Day

I'm trying to get a calculated column with MTD totals but hitting a wall and need help. Data mock up for my issue:



However, my code is duplicating the total for the day on each line:

MTDSales = 
VAR RowDate = SalesData[Date]
RETURN
	CALCULATE (
		SUM (SalesData[Sales]),
		FILTER (
			SalesData,
				SalesData[Date] <= rowdate&&  SalesData[Agent] = earlier(SalesData[Agent])
			)
		)

Results in...



- My actual dataset does span multiple months, so will need logic to take into account the month

- I'm using a calculated column because I will need use these totals for a separate measure (i.e. track how far an agent is above goal day once he hits goal)

New to PBI, any help is appreciated.