I'd like to add a symbol table to my math book. Since there is no meaningful/helpful way to order the index entries lexicographically, I'd like to order them chronologically, i.e. an index entry x will precede an index entry y if the first occurrence of x in the book precedes y's first occurrence. Is it possible to automate this kind of indexing using the MakeIndex program/makeidx package, or some other program/package?
P.S. To be more precise, I don't mean the absolute first occurrence of a symbol in the book; only those occurrences that I explicitly indicate should be considered.