I see/understand how to use the replace function.
Would still be interested in finding out if it is possible to add custom characters for the less common fractions (5/8, etc)
Also, would it be possible to construct a form to use for the repalce operations? For example: a simple form with to text boxes, one to type in the text to find and the other to type in the replacement text, then a button to run. Trying to find an easy way for a user to do find/replace on a field in a table - where there are several different things in a string to be replaced.