Using by statement in proc esm

I was using proc een in SAS, for time series forecasting. I want to include two variables in by statement. My data contains four columns:

1. Shop_id
2. Item_id
3. Item_price
4. Date

The item_price column is the one which should be forecasted. The date is in months. I want to include both shop_id and item_id in the by statement

Is it possible ?