For info, feedback welcome: I'm posting my calc (FM7 only) to clean up ISBN data entry. It adds dashes and verifies checksum. ISBN dash formatting is highly conditional -- and useful because the publisher code is the sequence up to second dash. Assume you have an isbn text field (must be text so as not to lose initial "0"), and you're working with English-language origin presses (though you can modify this for other ISBN standards). Have its auto-enter calc REPLACE existing value (uncheck DO NOT replace), and paste the following:

Let(F=Filter(isbn;1234567890)&Case(Right(isbn;1)="x";"X");

If(Length(F)<>10;"10 digits req'd ";

Case(Mod(Left(F;1)+2*Middle(F;2;1)+3*Middle(F;3;1)+

4*Middle(F;4;1)+5*Middle(F;5;1)+6*Middle(F;6;1)+

7*Middle(F;7;1)+8*Middle(F;8;1)+9*Middle(F;9;1);11)

<>If(Right(F;1)="x";10;Right(F;1));"Checksum FAILS "))

&

Left(F;1)&"-"&

Case(F<"020";Middle(F;2;2)&"-"&Middle(F;4;6);

F<"070";Middle(F;2;3)&"-"&Middle(F;5;5);

F<"085";Middle(F;2;4)&"-"&Middle(F;6;4);

F<"090";Middle(F;2;5)&"-"&Middle(F;7;3);

F<"095";Middle(F;2;6)&"-"&Middle(F;8;2);

F<"100";Middle(F;2;7)&"-"&Middle(F;9;1);

F<"186";Middle(F;2;5)&"-"&Middle(F;7;3);

F<"1999";Middle(F;2;6)&"-"&Middle(F;8;2);

F<"2000";Middle(F;2;7)&"-"&Middle(F;9;1); "INVALID?")

&"-"&Right(F;1)

)

Very nice. Thanks.