Chad,
Unless you are just trying to learn how to write macros, I would avoid using a macro for this problem. Instead, you can use proc sql to create a macro variable that does what you want. For example:
/* Create some test data */
data test2;
set sashelp.class (rename=(
name=row_labels
age=Col0001
height=Col0002
weight=Col0003
));
month=mod(_n_,3);
run;
/*Create a macro variable with proc sql */
proc sql noprint;
select "Sum ("||trim(name)||") as Sum"||substr(name,4)
into :sumCol separated by ","
from dictionary.columns
WHERE libname eq "WORK"
and memname = "TEST2"
and name like 'Col%';
quit;
proc sql noprint;
create table testMacro as
select row_labels, &sumCol.
from test2
group by row_labels,month;
quit;
HTH,
Art