I've been using this to prepend an area code - if one is supplied - to
a phone number:

Phone: { IF { MERGEFIELD AreaCode1 } "" "{ MERGEFIELD AreaCode1 }-"
"" }{ MERGEFIELD Phone1 }

Because I allow the user to select the type of contact information on
the input form, I wrap the above within another conditional:

Phone: { IF { MERGEFIELD Type1 } = "Phone" "{ IF { MERGEFIELD AreaCode1
} "" "{ MERGEFIELD AreaCode1 }-" "" }{ MERGEFIELD Phone1 }" "" }

Not too elegant, but it works. Or at least it did, until two weeks ago.
Suddenly, on a single client machine (XP Pro, Office 2002), area codes
refuse to print. I've copied the data source to several other computers
and enviroments, and all is ok. I'm baffled. Can anyone think of any
sort of MS update the client might have loaded that could affect this?