[R] Planned contrast on repeated measures

[Ryan Hope]

I have an anova model that looks like this:

aov(log(Y)~X+Error(Participant/X))

Is there a way to do a planned contrast on a repeated measures
model... something with an error term? I get an error when I do this:

contrasts(X)=cbind(-3,-1,1,3)
summary.lm(aov(log(Y)~X+Error(Participant/X)))

Any help would be appreciated!

-Ryan