Concatenate returning distinct values

Hello everyone,

I have a measure in a table that gets the concatenation of values in a different table:

ScheduelStartDates = CONCATENATEX('tct_schedule',DAY('tct_schedule'[CourseStartDate]),",",DAY('tct_schedule'[CourseStartDate]),ASC)

Works well, but since I have many days that are the same, I get an repetition of same values

e.g. 1, 1,  and 11, 11 etc.

I only need to get the distinct days ie 1,2 ,4

therefore i need something like

ScheduelStartDates = CONCATENATEX('tct_schedule',DAY(DISTINCT('tct_schedule'[CourseStartDate])),",",DAY('tct_schedule'[CourseStartDate]),ASC)

This doesn't work.

I have tried moving DISTINCT earlier.. doesnt work either.

Help would be appreciated!