[lattice] how to label panels with variable value (not name)?

I [can now] prepare my netCDF data specifying gas concentrations over
a 3D space (dimensions longitude, latitude, and (vertical) level),
so as to call lattice::levelplot() like

levelplot(conc ~ lon * lat | lev, data=data.frame)

However I will need to [do before-and-after comparisons of that plot]
to the results of a reboxing, or 3D regridding, of this data[. Hence]
I would prefer instead to label each panel in the lattice with the
_value_ of [its] level (an atmospheric pressure), rather than [its]
name or index

see ?strip.custom in lattice