You are asking to override text for PMI dimension in Modeling or Drafting application ?
In drafting you can do it as to the normal dimensions from settings ( Text > Format > Override Dimension Text).
Testing: NX 11 | NX 12 | TCIN
TC 11.2 | TC Vis 11.3 | AWC 3.2
Why would you want to do that?
Overiding dimensions is generally a Pandora's box. I suspect you're trying to convey some other information using a dimension - what is it?