If you need to give your users the ability to select multiple OR no values within a selection box, the stored process needs to be capable of addressing this flexibility. For the example below, users wanted to choose 0 to 3 severities (of 4) to exclude from the results.
%macro datastep; data temp; set table name; /*test to make sure more than 1 severity was selected*/ %IF %length(&severity;) > 0 %THEN %DO ; /*test to make sure only 1 severity was selected*/ %if %SYMGLOBL(severity0) EQ 0 %then %do; if severity = &severity; then delete; %end; %else %do; /*runs the same code multiple times for each of the severities selected*/ %do i=1 %to &severity0; if severity = &&severity;&i; then delete; %end; %end; %end; %mend;