st: Propensity Score Matching Between 3 Groups

[ir w <iwilliams24@hotmail.com>]

Hi,

I am trying to estimate a propensity score and then find the 
average treatment effect on the treated. However, my sample has 3 
groups:

Group A: Resides in intervention area, receives treatment
Group B: Resides in intervention area, doesn't receive treatment
Group C: Resides in non-intervention area, doesn't receive treatment

This
 is effectively like having 1 intervention group and 2 control groups: I
 want to calculate a propensity score for treatment between Groups A and
 B. I then want to apply this propensity score to Groups A and C to find
 the average treatment effect on the treated. 

I have seen this 
done in several economic papers, but never explained thoroughly. Is it 
possible to do this in Stata, and if so, how?

If it is relevant, I am using a logit model and psmatch2 to estimate the propensity score.

Thanks! 		 	   		  
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/