Report Parameter And Multi Value Prompt

Hi all

Basically I had 2 paramater which ComputerName and MemberName.

The membername was set as Multi-Value as sets as follow:
Label: Value:
Exclude Domain Admins Domain Admins
Exclude Local Install Local Install

And the query is:

SELECT id,
ComputerName,
GroupName,
MemberName,
ScanDate
FROM GROUPMEMBERS WITH (NOLOCK)
WHERE ComputerCN LIKE '%' + @ComputerName + '%'
AND MemberName NOT IN (@MemberName)
ORDER BY ComputerName ASC

The prompt is like this:
Computer Name [ ] Excluded by [ ]

The issue is in the second prompt I have to select
"something" which is I don't want to. I want the user to have this parameter as an optional.

Any ideas?

Thanks