Reference date from a calendar table in a custom column

Hello all,

Pretty sure this is a straight forward answer I just can't seem to figure it out.

I have a custom calendar table that is fairly standard practice. It's a single column table with a bunch of dates that I can use as reference in measures. That works fine with measures, but is it possible to do the same thing for columns? 

I have a historical dashboard with a table that has all the historical data, and a column called "Snapshot Date" that has the date of the snapshot. The data also has a column "Date Created" that has the date created of a document.

I wanted to create a column that says if it was created within a week of a certain date in history. So something along the lines of:

IsWithinAWeek = IF(DATEDIFF(Table[Date Created], [SelectedDate], WEEK()) == -1, "Last Week")

Where [SelectedDate] = MAX(Calendar[Date])

This doesn't seem to be working. The actual implementation is a bit more complex that incorporates "Last week", "this week", and "next week", but this is the gist of it. 

EDIT: 

I forgot to mention, I'm doing this because I want the user to be able to use the calendar UI to pick a single date. So I'm doing the trick where you have a date slicer set to "Before", and I'm blocking the "After" side of the date picker and using MAX() to get the date. 

As such: