Ok, I'm looking to see if this is possible using AutoCAD 2012 LT.  Here's what I'm looking for:For the exterior elevation, the baseline/datum (finished floor) is 0,0, elevation marker has a field that reads the elevation from the y plane.  However, the interior elevation may have a higher finished floor level.  How can I get the elevation marker w/ a field that auto updates, to read off the 2nd finished floor elevation (or any baseline).  There may be several finish floor levels in one drawing.  Is there a way to define additional reference points?  I've included a sample to try to clarify what I'm seeking...

Hello HeatherH, I think that the AutoCAD command DIMORDINATE will be OK for you.
Eventually, see my DWG file : FEET-METERS.dwg that you can find in the CAD Blocks library right here in the site : Launch a search with : FEET-METERS.
It explains the use of alternative dimensions which is also your case but it includes the use of the command DIMORDINATE.
When you put a dimension with DIMORDINATE you will be abble to have dimensions in X direction and Y direction wich will be your choise.
This dimension have a grip at the 0,0 point and for you will have to set a zero on each floor to have 2 dimordinate correct dimentions.
Instead of setting a new UCS each time you want to dimension a ceiling you can copy a dimordinate allready made and GRIP A NEW THE GRIP OF THE 0,0.
To modify and have an automatic updating of the elevation DIMORDINATE you will have to use the command STRECH.
Ask for more and tell us if this helped or not.philippe JOSEPH2014-09-25 07:59:06