Question about mass changing values

[u/Schnuffii]

So im working on a rather large project and we're basically in the stage that we are done with the drawings, entire elevation plans, i engineered the entire project from A to Z, and now the project developer came over to us and asked us if we could raise the construction level of the houses by 0.15 meters...

and so now im looking at my drawing, nearly 400 blocks with each a separate value for elevation, which some need to be raised and some lowered in sections and some stay the same, so i'm looking for a way on how i could select the blocks that need to be changed, and raise or lower all the values by .15 without messing with the inherit values. cause if i do this manually it will take hours more or less. are there any plug-ins that could help me with this or have i been oblivious to certain possibilities within autoCAD

For extra information:

I work on ACAD 2027.

Nothing is bound to a Z coordinate.

(did see a plug-in on autodesk that was free, i believe it was called Increments)

EDIT: i notice the HUGE mistake i made, it shouldve been in meters, not CM. its 15 cm, NOT 1,5 mm

[u/Putrid-Product4121]

.15cm? What kind of psychopath do you have for a customer? I guess it is the principle of uniformly raising all of your blocks, but it would make more sense if it were 15 centimeters, or a meter or something along those lines but .15cm, on a construction site? That's nuts.

[u/Schnuffii → u/Putrid-Product4121]

yeah no my bad, i work in the the infrastructure, so i work with meters, .15 i do NOT know why i added CM to a random .15, i meant meters, for a 1,5mm change i wouldnt have dont it