That should do it: ^interface FastEthernet.+\nswitchport access vlan ((?![1][2][0-7])[1-2][2-9][0-9]|[2][0-9][0-9]|[3][0][0])
((?![1][2][0-7])
takes care of everything equal or below 127
[1-2][2-9][0-9]|
takes care of everything from 120 to 299 (120 to 127 is taken care of by the first negative lookahead)
|[2][0-9][0-9]|
takes care of everything from 201 to 299
|[3][0][0])
takes care of 300
Regards
Rene