Happy New Year to you all

I have a sheet that has a list of dates in column B, can be multiple instances, I have the following line that findes the end date based on a previously defined date
Columns("B:B").Find(what:=EndDate).Activate
this looks for the last working date of the previous month, but I've had a problem this month where that the 31st Dec doesn't not actually feature in my list, so I need something that will look for the MAX date in that previous month and use that instead.

any ideas please?