Do you mean Dynamic Posts? Or Fixed? Is your Railing attached to a Stair?
Or standalone?
In general, the answer is no, but you might be able to accomplish this using
the "Fixed post at Railing Corners" setting (on the Railing Style > Post
Locations tab). Note that you can also right click > Post Placement > Add
to put posts wherever you like. These posts stay a fixed distance from the
start end of the railing when you stretch it.
Hope this helps,
Bill Glennie
Autodesk Building Solutions Division