That's almost it except that that code matches indexes of each 'x' and 'y'. Below are successive 'do' loops that I've used to do the job, but I'm still trying to figure out how to input each 'varNames' into a matrix and eventually append that to some dataset as column names.

Proc IML;
Reset Log Print;
Do i = 1 to 5;
names1 = cat("x",putn(i, "BEST4."));
Do t = 1 to 5;
names2 = cat("y",putn(t, "BEST4."));
varNames = cat(names1,names2);
End;
End;
Quit;

Thanks for your help!