Move only one markup at the same place

[Bertalan Fodor (LilyPondTool)]

Hi, I have a note with two simultaneous markups:

c''^"A"_"B"

I want to move "B" to be right below the note and not below the staff.
How to achieve that without instantiating a new Voice containing a 
hidden note? I couldn't find any other solutions.

Thanks,

Bert