Goal: I want to subtract the results of "margins" from a constant.

My approach: Use margins with "at" and subsequently use "lincom" to do the subtraction. That's a bit cumbersome, because I have to address the results of "margins" manually (or in a loop).

Question: What's the easiest way to calculate multiple "lincom"s after the "margins" command with "at"?

Here's a toy example:

Code:
sysuse auto, clear

regress price mpg headroom trunk weight

margins, at(mpg = 20 headroom = 3 trunk = 14 weight = (1760(10)1800)) noatlegend post

lincom 3000 - 1._at
lincom 3000 - 2._at
Here, I simply want to subtract the resulting margins from a constant of 3000. If I wanted to do this for all calculated margins, I'd have to address all "_at" coefficients manually (or in a loop). Is there an easier way to do this?

Thanks for your guidance.