[texhax] detect characters in strings

[Brandon Kuczenski]

Hi folks,

Say I have a macro \mymacro which expands to a number, like 
'0.00346'.  Due to circumstances beyond my control, this macro sometimes 
contains something unsightly, like '3.46e-03', which causes later commands 
(in fp.sty) to barf.

Is there a way I can detect an 'e' in a macro expansion?

Thanks in advance,
Brandon