using the "-" symbol to refer to many datasets

Hello all,

hopefully someone can help understand why something is not working.

To summarize some background, I used macros and do-loops to create many datasets, for instance:

data2009_1_1
data2009_1_2
data2009_1_3
data2009_2_1
data2009_2_2
....
....
and so on.

As you can see there are 3 groups of numbers which are separated by underscores. What I want to do now is to merge datasets that have the same first 2 numbers. So, I want to merge data2009_1_1 data2009_1_2 data2009_1_3 with one another.

I know I could accomplish this with:

data merge;
merge data2009_1_1 - data2009_1_3;
run;

Hence, I could use the "-" symbol to merge a bunch of similarly named datasets whose number at the end increases by 1.

HOWEVER......sometimes I want to merge 4 datsets, sometimes I want to merge 2, sometimes I want to merge 5....it varies. So, what I did was to create a macro variable that found the maximum number of datasets that I want to merge. Essentially, my code to merge the datasets is as follows:

%macro pareto_merge(var=);
proc sql noprint;
select max(&var) into: maxvar
from obesity;
run;

%do k=2009 %to 2010;
%do j=1 %to 1;
data histomerge&k._&j;
merge &var&k._&j._1 - &var&k._&j._&maxvar;
run; quit;
%end;
%end;
%mend;

Where the &maxvar represents the highest number. However, it never seems to work and I get an error in the log saying it expects a numeric value where &maxvar is.

I know tha &maxvar = some number (for instance 4). If I replace &maxvar with 4, this code works - but I don't really want to have to specify a number since I want this process as automated as possible. Any suggestions (assuming anyone could actually follow my rambling) on why this wouldn't work?