[R] character string as object name

[Fuchs Ira]

Can someone please tell me why the following (last line) doesn't work  
(as I expect it to :-)

library(quantmod)
a = getSymbols("MSFT",from="2009-3-01")
a
MSFT
eval(as.name(a))
MSFT$MSFT.Adjusted
b=paste(a,'$MSFT.Adjusted',sep='')
b
eval(as.name(b))

Why does this last line not work the way the earlier eval does?

Thanks.