Column to Populate the MAX value

Hi, 

I have a column comp.description which has the following values: (BLANK, Test, Live, Failed).

I also have a date field comp_date_tested. 

What I would like to see the comp.description which has the MAX comp_date_tested BUT exclude BLANK and Test.  So my new column "latest_description" would show for all rows as "Failed" as that has the lates date/time that isn't a BLANK or Test.

Example

Any idea how to do this please?