scale caption on levelplot

hi,

i am trying to figure out how to put a caption on the colour scale of a
levelplot. there does not seem to be an option for this in levelplot().
i tried using mtext() but as soon as you put the text far out enough on
the right of the plot, it goes beyond the plot boundary. so i tried to
extend the margin on the right of the plot using par(mar) but this did
not have any effect on the plot area.

i would really appreciate some help with this because having a caption
on a colour scale is rather fundamental and certainly something that a
journal referee is going to pick up on!

best regards,
andrew.

Andrew B. Collier

Physicist
Waves and Space Plasmas Group
Hermanus Magnetic Observatory

Honorary Senior Lecturer                             tel: +27 31 2601157
Space Physics Research Institute                     fax: +27 31 2607795
University of KwaZulu-Natal, Durban, South Africa    gsm: +27 83 3813655