Is it correctly understood that your DPSX command adds texts to the properties TextPrefix and/or TextSuffix? If so, it results in creation of XData that overrides the parent dimstyle's DIMPOST variable.
Another method could be to use the TextOverride property. This will add text to group code 1 of the dimension's entity list. If it doesn't include "<>" then it will totally override the dimension text. If it includes "<>" then it will allow TextSuffix, Measurement and TextPrefix to show as well.