How to access vile variables in : command?

[Chris Green]

I'm sure this should be obvious but at the moment it's not obvious to
me! :-)

I want to do something like the following:-

    map #9 :e `pdf $cfilname`^M

However the above doesn't work, $cfilname is null in the above
context. How can I get the current file's name in this sort of place? 


-- 
Chris Green