Type III sums of squares for an anova with a missing cell

[Brett Lovelace <gulogulo@canopybio.com>]

I am trying to employ the ssType=3 argument to analyze a split-split 
plot 3 factor ANOVA for which I have a missing cell.  The help file for 
summary.aov that describes the usage of ssType=3 says that an aov or 
aovlist object is required.  When trying to run the aov command for my 
dataset, I get an error that indicates that I cannot use such a command 
with a data frame with missing values. 

How then do I get an aov file to calculate my type III sums of squares 
if I cannot run the aov command with missing values?  Any help would be 
greatly appreciated.