You could use a field coded as {EQ \o (~,m)}. To achieve the desired result, superscript the tilde in the field and subscript the m, which leads to small characters for both (which you could counter by increasing the point size), but this too increases the vertical spacing for the affected line.

Note: The field brace pairs (i.e. '{ }') for the above example are all created in the document itself, via Ctrl-F9 (Cmd-F9 on a Mac); you can't simply type them or copy & paste them from this message.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]