You might want to check out either MathType or MathMagic.
With MathType and InDesign, you can:
Add an equation to InDesign. You can save MathType equations as EPS images
that you can place in your InDesign document. You can also copy & paste
equations and expressions from MathType directly into InDesign.
Edit an equation in InDesign. If you use the Place command in InDesign, a link
to the equation is saved in the document. If you open the original EPS in
MathType for editing, after you have finished your changes, closing the window
will update the equation in InDesign.
Import a Word document with MathType equations into InDesign. If you
have a Word document with equations, save time by placing the document and
equations directly into InDesign, retaining proper vertical alignment on the
Both of these have versions for Mac & Windows,
Screen shots from Wikipedia:
Ellis is correct. It is done most easily using character styles for the super and subscripts, then kerning to move the sub under the super.
I read your post first over on the QuarkXpress forum and had answered it there. That reply also has a sample QXP10 file. the screen shot below is from QXP, but it works the same in ID. So grab the sample file and basically set up ID to do the same.