You could define a .shx font that simply draws nothing for the hyphen character. Assign that font to a Text Style, and assign that Style to a Dimension Style. [Presumably you would not use the font for any other purpose, because it would also draw nothing for hyphens in other contexts.]
Similar to what you will find >here<, with variants in other Messages in the same Topic. They are font definitions which draw nothing for the apostrophe [single-quote] and double-quote characters, at someone's request to not have the feet or inches marks in Dimension text [try it!].
But it has to be a .shx font, not a .ttf font, because the former can be edited that way with tools available in AutoCAD. The same kind of thing could be done with the hyphen instead being what is defined to draw nothing.
Kent Cooper, AIA