mister, that I know you can't set the model's measurement unit a priori, because this is inherent in your model. hypermesh supports more solutors and not all of them require measuring units, you are managing your model to intrinsically define it.
Suppose you pass a model, it amounts and measures the distance between two points, you expect it to be in mm and instead it is expressed in meters; in this case if you want the model in mm you should make a scale transformation from the tool menu --> scales, impose a uniform factor of 1000 and as a reference node the origin of the global system.
