As long as "Person 2" is a completely blank field (no spaces) if there is no
person 2, you should be able to use

{ MERGEFIELD "Person 1" }
{ MERGEFIELD "Person 2" }
{ MERGEFIELD Address }
{ MERGEFIELD City }, { MERGEFIELD State } { MERGEFIELD Zip }

The "suppress blank fields" option (which is switched /on/ by default)
should do the rest for you. If you are using Word 2000 or earlier, you can
ensure it is on using the Merge Options button in MailMergeHelper. However,
if the field is not completely blank, it will not be suppressed.

Also, if you are using Word 2002 or later,
a. you need to be using individual fields, as above, not the ADDRESSBLOCK
field
b. to use the (old) MailMergeHelper dialog box, you have to locate it in
Tools|Customize|Comands|All Commands and drag it to a menu or toolbar
c. if the mergefields are nested inside another field, suppression of blank
lines does not work.

If blank line suppression is not working, you have to do the suppression
manually using IF fields. In this case, try

{ MERGEFIELD "Person 1"
}{ IF "{ MERGEFIELD "Person 2" }" = "<put as many blanks as are actually in
a blank Person 2 here>"
"" "<put a paragraph mark here>{ MERGEFIELD "Person 2" }" }
{ MERGEFIELD Address }
{ MERGEFIELD City }, { MERGEFIELD State } { MERGEFIELD Zip }
--
Peter Jamieson
MS Word MVP