[OS X TeX] Referring equation into an .eps file

[Cleo]

Hi there,

I'm using originlab, excel, spss to produce some plots. In some graphics I refer
an expression on the legend (e.g. Error using expression (5.1)).
The problem is that, if I add/delete an expression in the .tex file before the
expression 5.1, the graphic becomes outdated and I have to manually change that
legend.

Is that a way of referring an expression  as part of the legend in an .eps
figure, and make latex to process it?

I'll appreciate your tips.