Vladimir, > there is a solution for this problem used in the mathtext package > available from > CTAN:macros/latex/contrib/supported/t2/etc/mathtext.{dtx,ins} > do you mind outlining the solution in a few sentences? how do you want to be able to find out that you are not in math but will be once something (eg tha actual letter) triggered the \halign u part without actually triggering it (with something like \relax which kills ligaturing)? thanks frank