I stand corrected. I've edited my above example although I recommend not using it. It is a not so trivial way around "pile" effect of lag function. It works though! Thanks Vince Here's the approach I would probably use similar to others above although saving the conditional if statement in favor of the coalesce function. data want;      set have;      total=value+coalesce(total,0);      retain total; run; ... View more