Distinct Count based on max value

Hey Everyone,

I'm having a little trouble with filtering by the maximum value of a month no. and wondering if anyone knows where I'm going wrong.

I have the following formula

Charities (Monthly) = CALCULATE(DISTINCTCOUNT(donation_event[recipient_id]), donation_event[Week No.]=max(donation_event[Week No.]))

Its just to get a distinct count of the recipients when the week no. is equal to the max value for the week no column and I am getting the following error.

"A function 'MAX' has been used in a True/False expression that is used as a table filter expression. This is not allowed."

Not sure where I'm going wrong as the below works fine too.

Charities (Monthly) = CALCULATE(DISTINCTCOUNT(donation_event[recipient_id]), donation_event[Week No.]=20))

Thanks