bootstrap vignette construction and package installation

hi all - i'm trying to 'R CMD build' a package, but i have what
appears to be a bootstrapping problem:
i've included a vignette in my package, with R code interwoven (and
built using Sweave), but in this documentation i have a code line:

library(MyPackage)

now, when trying to build a .tar.gz install-able version of my package
in a clean state, i remove the original compiled/installed package,
and the build fails because Sweave wants to execute the interwoven R
code even though the package hasn't yet been installed.

i got around it by temporarily just hiding the the inst/doc/
directory, installing the now-able-to-build package, then re-building
the package after the installation.
but this is a pretty clunky solution, and i imagine there's a more
elegant way to get around this bootstrapping problem that i'm just not
aware of.

any thoughts?

thanks much for any help,

-murat