Hello dear cad users.
I know the subject title is no good, but it didn't allow many characters.

Here's my problem :)

I made a drawing of a construction that i'm measuring some heights on once a week. It's some rails on which a big crane runs. This has to be level, but the ground is giving away,
so I measure one height at each end of each rail.
Now, I'd like to have an mtext field, or something similar, that updates when I enter a new height. Here's a schetch of the layout:

103.234        >12mm         103.222


So, I'd like to change the heights on the sides, and have AutoCad
calculate the difference between these two numbers and update the mtext in the middle. Anyone think it's possible?

And what about another way to update these heights in the first place?
Can anyone give me a hint if it is doable to connect a database to
a drawing, or if there's another easy way to manage these kind f numbers?

Many thanks in advance,

Tom E,
Oslo, Norway