markup height measured from staff?

[Monk Panteleimon]

Hello.

I would like to create a custom \markup command that puts a letter at a  
specified distance from the staff rather than from a note. It must be  
horizontally aligned with a note, but take its vertical position from  
the staff. I've looked through the \markup command overview and nothing  
seems to do that.
Any ideas?

Fr. P

--

        "There is no knowledge that is not impoverished,
         however great it may be; But heaven and earth
         cannot contain the riches of faith."
                                - St. Isaac the Syrian