On Tue, May 13, 2008 at 07:12:14AM +0000, Wolfgang Engelmann wrote: > by declaring a new command \Molek > \newcommand*{\Molek}[2]{#1\texstsubscript{#2}} > which I did by putting this in the preamble of my Koma-book document. > In the text I write in an ERT-box > \Molek H{2}
You probably want \Molek{H}{2} in the box instead. In any case, I find it easier (less and more convenient keystrokes) to simply type H <math-mode> _2 <space> directly in Lyx to accomplish the same thing, where <math-mode> is whatever keybinding you have to enter in-line math formulas and <space> is the space bar. YMMV.