Lag Column with Negative value?

I would like to reference the next (future) row, similar to how the Lag Column can reference the previous row.  This way I can measure if the next row will be different.  That way I can create something like this:

Mon      Name      Next      Last Mon

Jan      John      John      

Feb      John      Mike      Feb

Jan      Mike      Mike

Feb      Mike      Mike      

etc.

Essentially I would use a Java Snippet to see if Name.equals(Next), if not then that's the last month this rep is on record.