change default argument value built-in R function

Question

Possible Duplicate:
Setting Function Defaults R on a Project Specific Basis

I would like that when I call the built-in function table like this:

table(x)

the result be the same as if I call:

table(x, useNA='ifany')

i.e I don't want to explicitly set the argument 'useNA' every time I call this function.

More generally, how can we way to specify default behavior for built in function?