What I could get from your description, selecting a GROUPNAME would always match it to Parameter1 or Parameter 2 unless you set both Parameters at same value. Is n't it. So, I am little confused. Looks like you are already getting what you are looking for.
When I Choose one GroupName, the other one from the parameter will be gone due to the way I set my parameter. I can change the GroupName Filter to Mulitple values to have the both parameter showing. I don't want to do it this way. So my questions is that is there a way when I choose GroupName, it will only affect Parameter Variable 2, and Keep Parameter Variable 1 unchanged. Thank you!
Something I can do, but hope do not do it this way. Because the GroupName will be affected by an action filter from the dashboard.