Hi,
Your question is ambiguous, so I will give you two answers.
if you want to prevent the replacement from occurring, for example if you have foot [: x@n], and you want %mor tier to have n|foot instead of neo|x, then you need to replace foot [: x@n] with foot [:: x@n].
If you do not want EVAL to count neo|x at all, but only when it is part of replacement, the use option -sm|neo,;x,@* with EVAL. This option with exclude foot [: x@n], but will still count x@n when it is on a speaker tier by itself.
Leonid.