proc glmpower

data exemplary;
  do variety=1 to 2;
    do exposure=1 to 3;
      input height @@; output;
    end;
  end;
datalines; /* expected population means */
14 16 21 
10 15 16
run;

proc glmpower data=exemplary;
  class variety exposure;
  model height=variety|exposure;
  contrast "variety" variety 1 -1;
  contrast "exp 1 vs 3" exposure 1 0 -1;
  contrast "inter" variety*exposure 1 1 1, -1 -1 -1;
  power stddev=5
  ntotal=60
  power=.;
  plot x=n min=30 max=90;
run;