Yes... Quite an intriguing question.
Knowing the purpose would help, perhaps to point out another alternative.
Anyway, if I got this right, you want to reposition some observation within the dataset.
Being X=3 for example, you could try this:
[pre]
data OUTDATA;
set INDATA (where=(VAR ne 3)); * exclude the desired obs;
output;
if _N_ eq 6-1 then do;
set INDATA (where=(VAR eq 3)); * include the desired obs
output;
end;
run;
[/pre]
Cheers from Portugal.
Daniel Santos @
www.cgd.pt