Autorun when library("xxx") is called

Dear List Member

Is there a mechanism to automatically run a piece of R code when a 
package is loaded using library("xxx") ? Preferentially that piece of R 
code should be located inside the package.
I would like that this piece of code checks on a server if an update is 
available just at the time of package load (the package is not still in 
CRAN; it is a work in progress with several testers).

Thanks a lot for your advice,

Marc

__________________________________________________________
Marc Girondot, Pr

Laboratoire Ecologie, Syst?matique et Evolution
Equipe de Conservation des Populations et des Communaut?s
CNRS, AgroParisTech et Universit? Paris-Sud 11 , UMR 8079
B?timent 362
91405 Orsay Cedex, France

Tel:  33 1 (0)1.69.15.72.30   Fax: 33 1 (0)1.69.15.73.53
e-mail: marc.girondot at u-psud.fr
Web: http://www.ese.u-psud.fr/epc/conservation/Marc.html
Skype: girondot