In the case of numeric fields of up to 15 digits, not so. The problem here is the 16th digit, for which a suitable field construction is:

{QUOTE{SET Data {MERGEFIELD ACCOUNT_NUMBER}}
{IF{REF Data }= "*1???" 1 {IF{REF Data }= "*2???" 2 {IF{REF Data }= "*3???" 3 {IF{REF Data }= "*4???" 4 {IF{REF Data }= "*5???" 5 {IF{REF Data }= "*6???" 6 {IF{REF Data }= "*7???" 7 {IF{REF Data }= "*8???" 8 {IF{REF Data }= "*9???" 9 0}}}}}}}}}
{IF{REF Data }= "*1??" 1 {IF{REF Data }= "*2??" 2 {IF{REF Data }= "*3??" 3 {IF{REF Data }= "*4??" 4 {IF{REF Data }= "*5??" 5 {IF{REF Data }= "*6??" 6 {IF{REF Data }= "*7??" 7 {IF{REF Data }= "*8??" 8 {IF{REF Data }= "*9??" 9 0}}}}}}}}}
{IF{REF Data }= "*1?" 1 {IF{REF Data }= "*2?" 2 {IF{REF Data }= "*3?" 3 {IF{REF Data }= "*4?" 4 {IF{REF Data }= "*5?" 5 {IF{REF Data }= "*6?" 6 {IF{REF Data }= "*7?" 7 {IF{REF Data }= "*8?" 8 {IF{REF Data }= "*9?" 9 0}}}}}}}}}
{IF{REF Data }= "*1" 1 {IF{REF Data }= "*2" 2 {IF{REF Data }= "*3" 3 {IF{REF Data }= "*4" 4 {IF{REF Data }= "*5" 5 {IF{REF Data }= "*6" 6 {IF{REF Data }= "*7" 7 {IF{REF Data }= "*8" 8 {IF{REF Data }= "*9" 9 0}}}}}}}}}}

For a macro to convert the above into a working field, see Convert Text Representations of Fields to Working Fields in the Mailmerge Tips and Tricks 'Sticky' thread at the top of this forum:
https://www.msofficeforums.com/mail-...ps-tricks.html

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