st: detecting a dropped variable programatically

[Mark <statalist528h5q@feldmark.com>]

I am writing a program that runs through potentially tens of thousands 
of regressions.  During this evaluation, I sometimes end up with 
collinear variables.  (Not really, but very nearly collinear, and so 
numerically stata ends up thinking they are.)  I know that I can look 
thru the e(V) matrix looking for a value of zero on the diagonal.  But 
doing this for every regression means another loop inside the main loop 
that may run tens of thousands of times.

Does anyone know of a way to detect a dropped variable without a loop?

What would be nice is if the regression routine would return an 
indicator of a dropped variable.  But I dont see this, nor any obvious 
way to find it based on the return values except for searching thru 
e(V).  Any ideas appreciated.

Thanks!

Mark
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/