Calculate the max value reached in previous weeks (current week not included)

Hello,

I would like to calculate the difference between the MAX value reached in current week and the MAX value reached in previous weeks (current week not included). I am using a WEEKRANK measure to identify weeks and i created the following code. However I do not know how to exclude the current week from the "allweeks" variable.

%CHANGE_MS = 
VAR thisweek = CALCULATE(MAX(GPS[Max. Speed]),FILTER(ALLEXCEPT(GPS,GPS[Player Nickname]), GPS[WEEKRANK]=MAX(GPS[WEEKRANK])))
VAR maxweek = MAX(GPS[WEEKRANK])

VAR allweeks = CALCULATE(MAX(GPS[Max. Speed]), ALLEXCEPT(GPS, GPS[Player Nickname]))
RETURN

DIVIDE(thisweek-allweeks,allweeks)

Thanks in advance!

SQ