You could use data validation with a formula of
=AND(LEN(E1)=15,OR(AND(LEFT(E1,3)="LMN",MID(E1,4,5)="00000",ISNUMBER(--RIGHT(E1,7)),LEN(RIGHT(E1,7))=LEN(SUBSTITUTE(RIGHT(E1,7),"0",""))),
AND(LEFT(E1,3)="KLM",MID(E1,4,7)="0000000",ISNUMBER(--RIGHT(E1,5)),LEN(RIGHT(E1,5))=LEN(SUBSTITUTE(RIGHT(E1,5),"0","")))))
--
HTH
Bob
(there's no email, no snail mail, but somewhere should be gmail in my addy)
