R help - Feb 2008 - repeated measures ANOVA using a covariance matrix

Dear all,
how can I perform a repeated measures ANOVA using a covariance matrix as input?
E.g., I have four repeated measures (N = 200) with mean vector tau (no
BS factor):

tau <- rbind(1.10, 2.51, 2.76, 3.52)

and covariance matrix (sigma):

sigma <- matrix(c(0.523, 0.268, 0.267, 0.211,
                           0.268, 0.444, 0.492, 0.571,
                           0.267, 0.492, 1.213, 1.112,
                           0.211, 0.571, 1.112, 1.811), nrow = 4, ncol
= 4, byrow = TRUE)

Thank you very much in advance!