If it is Word 2003 (not sure about earlier versions) then
a. you will probably need to use individual fields rather than an
ADDRESSBLOCK field.
b. Suppose the field you want to test is called mytest and the first line
of the label needs to contain the text "abc"

Then insert the following merge field by hand, i.e. using Ctrl-F9 to insert
the special field braces {}

{ IF "{ MERGEFIELD mytest }" = "EA" "abc" "abc" }

Select the first abc and use Format|Borders and Shading|Shading to select
the background colour and ensure that the "Apply To" box contains "Text".
Notice that this will only apply shading to the part of the line containing
text. If you need to apply the colour to the whole line then you need to
insert a paragraph after each abc (before the quote mark) then select the
first abc<paragraph mark> and use Format|Borders and Shading|Shading to
select the background colour and ensure that the "Apply To" box contains
"Paragraph"

If the thing you need to display is the result of a field such as {
MERGEFIELD myfield } then you would use something like

{ IF "{ MERGEFIELD mytest }" = "EA" "{ MERGEFIELD myfield }" "{ MERGEFIELD
myfield }" }

(where all the {} are inserted using ctrl-F9)

and select the entire MERGEFIELD field rather than abc.

Peter Jamieson