mark a specific combination of two variables next to each other

[MABRINCH]

Can someone help me with a SAS code where a variable, MET, indicates if one of the variables CODE_1-CODE_44 contains one of several codes (T1b, T4a, T3a) and that the subsequent variable (of CODE_1-CODE_44) contains one of several codes (M1, M2, U3). 

CODE_1  CODE_2 CODE_3 CODE_4 .....        MET

T1b             M1            C2a         P4                      1

T4a             M4            C2a         T4a                     .

T4a             M4            T1b          M1                     1

[PaigeMiller]

UNTESTED CODE

data want;
    set have;
    array c code_1-code_44;
    met=.;
    do i=1 to dim(c)-1;
        if c(i) in ('T1b','T4a','T3a') and c(i+1) in ('M1','M2','U3') then do;
            met=1;
            leave;
        end;
    end;
    drop i;
run;
        

[mkeintz]

This too is untested, in the absence of sample data in the form of a working data step:

data want (drop=i _:);
  array search_strings {9} $8 _temporary_;
  length _part1 $3 _part2 $2  _code_string $200;

  if _n_=1 then do _part1="T1b","T4a","T3a";
    do _part2="M1","M2","U3";
      i+1;
      search_strings{i}=catx('!',_part1,_part2);
      put i=  search_strings{i}=;
    end;
  end;

  set have;
  _code_string=catx('!',of code_:);
  met=0;
  do i=1 to dim(search_strings) until (met=1);
    if findw(_code_string,trim(search_strings{i}),'!')>0 then met=1;
  end;

run;

This works by forming an array of compound terms to search for - each compound term (for example "T1b!M1") formed by concatenating one of the _PART1 expressions followed by a "!" followed by one of the _PART2 expressions - nine compound expressions in your case.  The array is declared as _TEMPORARY_ meaning it will not be output, but will be retained throughout the data step.

Then do a similar concatenation of the 44 CODE_ values, also with '!' as a separator.  Search that concatenated string for each of the 9 compound search terms until there is success, or you've exhausted the search terms.

Make sure you declare sufficient LENGTHs for the array elements and the other needed variables.