find value one row in advance of specified value

[broer konijn]

I would like to know how I can work with a vlookup kind of function in which I try to lookup a value that is ocurring one row above or below the 'specified value'.

Example:

I have a list of data and values

01/01/2000 value x
02/01/2000 value y
03/01/2000 value z

Now I would like to make a lookup for the value of the cell one row above 03/01/2000, so it returns value y from the line in which 02/01/2000 is the date.

I am also interested in a way to do this with returning a value one row below, but I guess that should be similar.

I would like to restrict the problem in the following way: sollutions cannot be:
-refering directly on the 01/01/2000 row
-referring to the date 02/01/200 and to do -1 (as the Excel number of the date-1).
Both solutions could be a work-around but do not work for the issue I am trying to solve.

Reasons are quite complicated to explain, but it should work as described above. Does it exist and can someone help me?

Thanx!