CODE EXAMPLE FOR JAVASCRIPT

regex more than one character

^                    Start of string/line anchor.
[A-Za-z]             First character must be alpha.
( [A-Za-z]{2}        Second/third character are either alpha/alpha,
 |[A-Za-z][0-9]       alpha/digit,
 |[0-9]{2}            or digit/digit
)                      (also guarantees minimum length of three).
[0-9]{0,6}           Then up to six digits (to give length of 3 thru 9).
$                    End of string/line marker.