[R] Pairwise comparison of proportions

[S.C. Wong]

I have collected the following data before and after a treatment for a 
number of sites:

	Before Treatment		After Treatment
Case	success	failure		success	failure
1	nbs1		nbf1		nas1		naf1
2	nbs2		nbf2		nas2		naf2
3	nbs3		nbf3		nas3		naf3
.....
N	nbsN		nbfN		nasN		nafN

I would like to do a "pairwise" comparison of the two proportions of 
success before and after the treatment to test whether the treatment is 
effective.

I am wondering if there is any R package that can help conduct this analysis.

May I thank you in advance for your kind help and advice!
SC