There is no way to do it in standard TEXT.  However you can do it in MTEXT using the stack mechanism.  As an example bring up the MTEXT editor dialog and paste in something like:

Raise to the 3rd^   Power!

Basically the formula is to use the ^ carat symbol along with the same number of spaces as you have characters to shift up/down.  In my example above I would enter this into the MTEXT editor dialog box, there are three spaces after the ^, two to balance the shift of the 'rd' and a third for the natural space between the words.  In the MTEXT editor I would highlight the 5 characters "rd^ ", then press the A/B stacking button in the dialog. The 'rd' then becomes superscript.  To achieve subscript simply reverse the order putting the spaces and carat first, for example " ^rd"."