[texhax] Making an index in TeXShop

[Firestone, Elaine R. (HQ-279.0)[SCIENCE SYSTEMS AND APPLICATIONS INC]]

My customer needs to have an index made in a report he's doing. He's using Plain TeX within TeXShop. Using MakeIndex is obviously not possible because that's only for LaTeX documents and that's not an option so please don't suggest that. ;-)  Does anyone know of a program that will automatically index a Plain TeX doc within TeXShop?

Thanks.

Elaine