how to calculate attributable risk in pspp

[Dr. Soumalya Ray]

hello friends,
i am preparing a presentation on measures of association. during the 
presentation, i started wondering about calculating attributable risk in 
pspp.
i am aware that risk under statistics under Analyze -> Descriptive 
statistics -> Crosstabs provides an estimate of relative risk and odds 
ratio (depending on the situation). however, i do not know how to 
calculate attributable risk.
how could i calculate attributable risk in pspp?

P.S.
1) i am attaching an example file with this mail. for calculating 
relative risk or odds ratio, i am using the following syntax:

CROSSTABS
        /TABLES= Smoking        BY       CHD
        /FORMAT=AVALUE TABLES PIVOT
        /STATISTICS= RISK
        /CELLS=COUNT ROW TOTAL.

2) attributable risk (AR)
AR= incidence of the disease among (exposed - nonexposed)/ (incidence of 
the disease among exposed)

regards,

som

example.sav
Description: application/spss-sav