Coefficient constraint

[zsears]

Hi, I am running a pooled regression, pool is called geo:

geo.ls(cx=f) log(y_?) log(x1_?) log(x2_?) @cxreg log(x3_?)

and I want to constrain the coefficient on x3 to be >0.

I have seen the other posts on constraints, but I cannot figure out a 'hack' for this.

Any suggestions on specification?

Thanks for any ideas.

ZHS