Histogram in Lattice with 3 factors

Dear R-help list,

I am trying to construct a lattice histogram using 3 factors.

My dataframe looks like this: (simulating a waterbalance over
groundwater with different salinities)

s      days   model    EC    EC_max
0.4     1        "A"       10      9
0.42   2        "A"       10      9
0.44   3        "A"       10       9
  :        :          :           :         :
0.4      1        "B"      10      9
  :        :          :          :         :
0.4      1        "A"      30        9
  :        :          :          :           :
0.4      1        "A"      30        36

Anyway you get the gist
EC_max has two levels 9 and 36, EC has 3 levels 10, 30 and 70, and
model has two levels ("A" and "B"). There are say 365 days and s is
the variable of interest (soil saturation)

Can maybe be reproduced with:
data <- data.frame(s = rnorm(2*3*365*2),rep(1:365,12), model =
sort(rep(c("A","B"),6*365)),
            EC = rep(sort(rep(c(10,30,70),365*2)),2), EC_max =
rep(sort(rep(c(9,36),3*365)),2))

I would like to plot histograms with the three factors using Lattice
so I had the following code:

my.strip <- function(which.given, ..., factor.levels) {
            levs <- if (which.given == 1)  c("Model A","Model B")
                    else {if(which.given == 2) paste("EC =
",as.character(EC),"dS/m")
                      else paste("ECmax = ",as.character(EC_max),"dS/m")}
            strip.default(which.given, ..., factor.levels = levs)
         }

histogram(~s|model*as.factor(EC)*as.factor(EC_max),data=Store,xlab="soil
saturation",type="density",strip=my.strip)

But I am doing something wrong, because it plots the histogram for
factor level EC_max =9 first and than straight over it the histogram
for factor level 36, so only 6 panels on the graph rather than 12.

I searched the archives, but no luck so far.