[R] plotting region

[array chip]

Hi, I have been playing with graphic parameters to
meet my specific plot requirement. I would like to
draw a plot in the top right region of the plot
region, I can do that with a number of parameters such
as plt, mar or oma. For example setting the
parameters:

par(plt=c(0.28,0.956,0.25,0.9))
or
par(mar=c(10,8,4,1))

can do the job. But once I set those parameters, I
could't add any text in the extra space left at the
bottom left regions. Actually, S-plus allow me to add
text in these white spaces, does anyone know how I can
do that in R?

thanks