how to find address of a range of cells that contain a value closest to a given value?

Hi,
I am using Excel 2007 and I'm trying to write a formula that will locate and provide me with the address of the cells that contain values closest to my given value.

for example if my given value is 1604...and in column A I have the following values...

A1 1585
A2 1590
A3 1595
A4 1600
A5 1605
A6 1610
A7 1615
A8 1620
A9 1625

i would like a formula that returns A4:A5


"Close in value" means the two closest cells that contain a value closest to my given value. First cell that is => my given value and first cell that is =< my given value

also I should mention i would like this to be something that is done dynamically... the values in my spreadsheet are updating in real-time

thanks