I've got an array function working that filters data by a certain
specified date (Dates!A1) and then returns the median for that fitered
subset of data.
See below:
={MEDIAN(IF(Data!$A$1:$A$200=Dates!A1,Data!$B$1:$B $200,""))}

I would like to extend it so that, rather than calucalting the median
for all data that equals a particular date, it would calculate the
median for all data that does not equal a number of dates. For
instance calculate the median for all data in column B where all the
dates in column A do not equal bank holidays as defined in Dates!
column A.

Cany anyone suggest how to do this?
Cheers
Matt