写了一段宏程序，怎么调试都得不到结果，很头大，求助各位大虾。程序如下,当N=1时，sum_drugs_&y.M_sum_drugs_&x.M就变成sum_drugs_6M_sum_drugs_3M，这个变量数据库自带并且是数值型。但是每次运行的时候，就说 A character operand was found in the %EVAL function or %IF condition where a numeric operand is required. The condition was:      sum_drugs_6M_sum_drugs_3M。也就是说sum_drugs_6M_sum_drugs_3M不是数值型！！不知道怎么回事啊~~

%macro drugpoint(N=);
%do i=&N %to 7;
    %let x=%eval(&N*3);
    %let y=%eval((&N+1)*3);
    %let drugs_ab=%eval(sum_drugs_&y.M_sum_drugs_&x.M);
   %if &drugs_ab=1 or &drugs_ab=-1  %then %do;
    %if B_B_&x.M_c ~= B_B_&y.M_c %then IOP_B_B=IOP_&y.M-IOP_&x.M;
%else %if  PGA_&x.M_c ~= PGA_&y.M_c %then IOP_PGA=IOP_&y.M-IOP_&x.M;
%else %if  Miotic_&x.M_c ~= Miotic_&y.M_c %then IOP_Miotic=IOP_&y.M-IOP_&x.M;
%else %if  CAI_&x.M_c ~= CAI_&y.M_c %then IOP_CAI=IOP_&y.M-IOP_&x.M;
%else %if  Diamox_&x.M_c ~= Diamox_&y.M_c %then IOP_Diamox=IOP_&y.M-IOP_&x.M;
%else %if  Adren_&x.M_c ~= Adren_&y.M_c %then IOP_Adren=IOP_&y.M-IOP_&x.M;
   %end;
%end;
%mend  drugpoint;