[OS X TeX] How specify .ist for index?

[Murray Eisenberg]

How does one go about specifying a .ist file to be used when makeindex is run automatically from within TeXShop?

(In my .ist file I use the usual settings so that each letter of the alphabet is typeset large and bold just before all the index entries that start with that letter.)

---
Murray Eisenberg                     murrayeisenberg at gmail.com
80 Fearing Street                      phone 413 549-1020 (H)
Amherst, MA 01002-1912