As others have pointed out, your best solution would be to actually define a macro, so that you can use %IF %THEN statements. As Tom hinted, in this case you could get by with a simpler solution as well by adding double quotes to your comparisons: if "&nton" = "yes" then do; ... if "&nton" = "no" then do; ... It will run a bit slower (and will make others question your macro language skills), but it will get you past the immediate problem. Good luck.
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