Retrieve data based on latest week value in a field

[#1]

I am loading an excel file which contains a week field and a phase field.  I want to build a chart that uses a calculated expression where it uses the value of the phase for the latest week.

[#2]

I need to find the function to use to retrieve the latest week from a table containing a few different dates.  Example below.  I tried using max(week) as [latest week] but get invalid expression error

[Week]

5/31/2013

6/7/2013

6/14/2013

6/21/2013