I have a time series data set of over 3,000 observations. I am trying to create a new variable that is dependent on that variable's previous value and I am having trouble getting SAS to calculate each observation in order to ensure that the previous value is calculated before it gets to the next observation. 

I have set the first observation to 1. Then for the remaining observations I want SAS to calculate:

New\_var = lag(new\_var) \* (1 + Var2)

Any ideas? I am sure it is a relatively easy answer, but I haven't been able to decipher it myself.