Nexus/lexus:
The 'measure' command almost gives you what you want. It places points along a line/arc/pline at intervals you specify. If you had a 3-d line or arc the points would be placed at a 3-d spacing and would vary in elevation per location on line. So you could pre-calculate the required 3-d spacing that would give you correct 2-d spacing, then use that spacing with Measure. But if you 'Measure' an entity of constant elevation, such as a 2-d polyline, the points will be placed correctly but you'd have to manually set elevations. Depending on your needs, a custom routine may be called for.
Carl