You could try:
{EQ \o (-,4)} or {EQ \o (-;4)}
as appropriate, where the - is superscripted and the 4 is subscripted, substituting + for - when required. Adjusting the point size can also be used to increase/decrease the size of the characters together or independently.

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