[R] Goodness of fit for hclust?

[dhinds at sonic.net]

I'd like to get a measure of goodness of fit for a heirarchical
clustering result from hclust.  Something that would indicate the
extent to which the dendrogram accurately represents the original
dissimilarity matrix.  Is there an easy way to do this?

Or, does anyone have code for computing distances between nodes given
an hclust structure?  So far, my searches have come up dry.

-- David Hinds