Numerical precision problem

Dear All,



I have a numerical problem:

R, as other statistical software, can tell the difference between very 
small numbers and 0, while apparently cannot distinguish a number close 
to 1 and 1. In the example below, is it possible to instruct R to 
recognize that q is different from 1?

q==1

[1] TRUE

The main problem I have is that I need to evaluate the inverse of the 
normal Cumulative Distribution Function near 1 (but not exactly 1) and 
the PC cannot recognize it.

p=.00000000000000000000000000000001
p

qnorm(p,lower.tail=FALSE)

-qnorm(p)