Below is a sample of my dataset:

Within in the variable "Country" I have countries belonging to Group A, and Group B (dummy variables).
I want to do a panel regression in SAS on the returns of these countries as such:
model Returns = Event(0,1)
with the added condition that, for example,
I only want to consider countries belonging to Group A, and during a Pre-2000 period.
Is there a way to code that in SAS using this current dataset?