st: St: I am using a model with interactions. How can I obtain marginal effects

[=?gb2312?B?0+Ag0evR6w==?= <yuyangyangkitty@hotmail.com>]

hello:
  According to the 
http://www.stata.com/support/faqs/stat/mfx_interact.html,the author tells 
me how to obtain marginal effects and their standard errors. So I program, 
the code is following:
(Note:  h is the dependent variable ,  pcinc  ratio1 ii1 is the 
independent                variable ,furthermore , ii1 is the interaction 
term.)
probit h  pcinc ratio1 ii1
quietly summarize  pcinc if  e(sample)
local meanpcinc = r(mean)
quietly summarize ratio1 if e(sample)
local meanratio1= r(mean)
local xb  _b[pcinc]*`meanpcinc '+_b[ratio1]*`meanratio1 '+_b[ii1] 
*`meanpcinc '*`meanratio1 '+_b[_cons]

(The above step is ok in stata)

predictnl dydt=  normalden(`xb')*(_b[pcinc]+_b[ii1]*`meanratio1')in 1 
,se(sep)

��invalid syntax�� appears in stata. I don��t know what��s wrong with this 
step .so could you help me to solve this problem. Look forward to your 
reply ,

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