I strongly suggest providing an example data set and then show us which of the percentages that will appear in Lab_id that you are asking about.
Here is an example of creating a data set with the output percentages that you should be able to run to see what I mean:
proc freq data=sashelp.cars ;
table origin*make*type/out=work.percent outpct ;
run;
Then it may be time to discuss how you intend to use that list of variables. it may be better to generate a data set(hint: likely needed for the macro approach) and use the values in the data set.