axes in boxplots

Hi

I am struggling with controlling the axes of boxplots. I need to produce 
two horizontal boxplots with the same x-axis for comparison purposes.
But when I generate a plot(c(-12,8), c(-6,1), type="n") first, then the 
following boxplot always overwrites it! I went into the code of 
boxplot.default, but even that without success.

Thanks for any hint!

David