Variable variables

I have the following code .............

echo $b[holdnavn]     //outputs "Denmark"
echo $a[Denmark][score]    //outputs "5"

Now i would like to include $b[holdnavn] in the second, like this: $a[{$b[holdnavn]]}[score], which should output "5". I have looking at http://www.php.net/manual/language.variables.variable.php the last part, and tried that, but could not get it to work. How am i doing wrong?. Best Regards Adam Helms