"object not found" within function

Hi,

I am trying to write a function to compute many cross-tabulations with 
the -svytable- command. Here is a simplified example of the structure of 
my code (adapted from the -svytable- help file):



data(api)
func.example<-function(variable){ dclus1<-svydesign(id=~1, 
weights=~pw,data=apiclus1, fpc=~fpc)

svytable(~ variable, dclus1)

}
  When I call this function with:

func.example(api99)

I get the following error:


Error in eval(expr, envir, enclos) : object 'variable' not found.
(Everything works fine when I type svytable(~ api99, dclus1).)

I guess that the problem has something to do with function environments, 
but since I am new to R, I can't seem to figure out how to rectify the 
code.
I am running R version 2.10 on Windows Vista.
Thanks for the help!

Thushyanthan