[R] problems with axis

[nelson -]

hi list!

i'm plotting a probit plot .On x axis i have value of a statistical
variable. on y axis the corresponding normalized representation. I
have this code

   plot(vals,perc,axes=F,col="red",pch=19,cex=0.25)
    probit.scale.values <-
c(0,0.001,0.01,0.05,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,0.95,0.99,0.999,1)
    probit.scale.at <- qnorm(probit.scale.values)
    probit.scale.labels <- format(probit.scale.values,digits=3)
    axis(2,at=probit.scale.at,labels=probit.scale.values,las=1)
    axis(1)
    grid()

now the grid is misplaced. How can i set up where ticks have to be
plotted? Here it seems the grid isn't affected by the axis() call...
Another question: how can i set up a subtick division in another color
and plotting the relative grid on the same plot (like major and minor
tick)?

thanks for any advice,
  nelson