Regular Expression for character combinations or strings that should NOT match

http://msdn2.microsoft.com/library/bs2twtah(en-us,vs.80).aspx

(?! )

Zero-width negative lookahead assertion. Continues match only if the subexpression does not match at this position on the right. For example, \b(?!un)\w+\b matches words that do not begin with un.

Combined with an alternation construct:

http://msdn2.microsoft.com/library/36xybswe(en-us,vs.80).aspx

|

Matches any one of the terms separated by the | (vertical bar) character; for example, cat|dog|tiger. The leftmost successful match wins.

280Z28 at 2007-9-9 >

\b(?!XX[^A-Z])[A-Z]+\b

would match all codes that can be formed by the letters A-Z except for XX.

you can replace "+" with "{1,3}" if the codes can only be 1-3 letters:

\b(?!XX[^A-Z])[A-Z]{1,3}\b

to do the same, except this time match all 1-3 letter codes except VY and XX:

\b(?!(?:XX|VY)\b)[A-Z]{1,3}\b

280Z28 at 2007-9-9 >