proc freq/ odds ratio/ categorical variable

hello,

below is the code i am using.

nativity= foreign born - yes or no
agegroup20 - 20-39, 40-59, 60+

proc freq data=work.hanes_formates order=data;
tables nativity*agegroup20 / chisq relrisk;
exact pchi or;
run;

the question : can a reference group be assigned to the categorical variable(agegroup20) so that multiple odds ratios(in this case two) are generated, using agegroup 20 (20-39) as a reference category?

if not possible how could i accomplish this (other than hand).

thanks for all the help