How do you look up a value in colum a and find the nearest match in colum b.

Colum A Colum B
Joe 10/16/2004
Joe 5/17/2004
Mary 1/8/2004
Mary 3/12/2004

If I had a name in another worksheet and was looking for the name & date
that most closely matched it. (joe 10/01/2004). vlookup just gives the
first one. I don't need to have both dates returned.