nlme : how to obtain confidence intervals of fitted values

Hi

I used lme (from package nlme) to fit a model containing two fixed factors, one random factor and a variance function (weights=varIdent(form=~1|as.factor(year_collected)). This is my "best" model.

I would like to plot the confidence intervals for the predicted fitted values. Something similar to se.fit=True in predict.lm but for lme models containing random effects and variance function.

Does anybody knows how to do this with R ?

Thanks
Laura