Possibly, Jeroen Weesie's -linest- maybe of use:
TITLE
linest. Two-stage linear-constrained estimation.
DESCRIPTION/AUTHOR(S)
linest imposed linear constraints on the last estimation
results. This two-stage estimator is asymptotically equivalent
to the "true" one-stage constrained estimator.
If anyone else is interested in this neat little command - as far as I can
tell, it produces the same coefficients and test statistic that you get
from using the -test- command with the -coef- parameter. Its biggest
advantage over -test-, at least that I can see, is that it lets you replace
the values stored in memory from the unconstrained model with the values
from the constrained model. This is very useful for post-estimation
commands such as -predict- or -fitstat-.
