Dynamic function names

Is this possible to do with XQuery? I'd like to be able to eval() a function whose name I'm getting from a variable. In a nutshell, I would have an attribute whose value is the function name that needs to be called. Something like:

                let $func_name := //blah[@function_to_run]
                let $func_argument := //blah[@some_id]
                let $result := eval($func_name( $att_value ))

which would basically execute the function whose name is $func_name, passing it $func_argument as the only argument and storing the result in $result. Of course, the 3rd line does not work and it's only to show what I'm trying to accomplish. Is there any way to accomplish this, not necessarily using eval()?

Any help will be greatly appreciated!

-i