See: http://office.microsoft.com/en-us/wo...005186172.aspx

If using Windows, for such a case you might delete the paragraph break after Add_2 and add a \b switch to 'Add_3', thus:
{MERGEFIELD Add_3 \b ¶}
where the ¶ is an actual paragraph break. To add the switch, select the «Add_2» field and press Shift-F9 to expose its code. Press F9 again when you're done.

If using a Mac, for such a case you might delete the paragraph break after Add_2 and code an IF field thus:
{IF «Add_3» <> "" "¶«Add_3»}

Note: The field brace pairs (ie '{ }') for the above examples are created in the body of the document via Ctrl-F9 (Cmd-F9 on a Mac) - you can't simply type them or copy & paste them from this message. Likewise, you can't type or copy & paste the chevrons (ie '« »') - they're part of the actual mergefields, which you can insert from the mailmerge toolbar. Instead of the ¶, you should use a real line/paragraph break.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]