Position measure is a distance-measuring script for 3ds Max, written by Chuggnut. Select two objects and it returns the distance between them. With a single object selected, it instead measures the distance between two of that object's vertices. Which measurement runs depends on the selection you have active.
Each result is reported in the prompt line, keeping the readout inside the 3ds Max interface. Position measure is a small, single-task utility rather than a full measuring suite, and it is offered here at version 2.3.5.
The script is catalogued in the ScriptSpot library and comes from Chuggnut. It is listed as a free download. For the current release and any accompanying details, the developer's page at chuggnut.com is the place to look.