Dan, the find command is truly an amazing tool if you know how to use it. In Mtext, stacked and diagonal fractions are created by using x#y for horizontal and x^y for diagonal fractions. Therefore, all you have to do is find all mtext items with # and replace them with ^. You can filter what find looks for by selecting the options button and deselecting everything except mtext. Also, if you select the button next to the Search in: pulldown, you can select which items this would apply to.