print value of variable to screen or alert box?

I am trying to debug a loop. Is there a way to print the value of a  
variable
that is inside a loop? I have a vector v and inside a loop I have  
v[i] where
i is the index of the loop. Is there a way to see v[i] per loop so  
that I
can see what is going on?
Thanks
-- 

> v <- vector()

 > for (i in 1:5) { v[i] <- i^2; print(v[i])}
[1] 1
[1] 4
[1] 9
[1] 16
[1] 25

 > for (i in 1:5) { v[i] <- i^2; print(paste(i, " squared = ", v[i]))}
[1] "1  squared =  1"
[1] "2  squared =  4"
[1] "3  squared =  9"
[1] "4  squared =  16"
[1] "5  squared =  25"

David Winsemius, MD
Heritage Laboratories
West Hartford, CT