Yes. And there are multiple options for doing so.
ExecuteSQL is one option. A WHERE clause can include logic that excludes those records were ex_name = 'exclude'.
A relationship can be set up that only matches to records if ex_name is not "Exclude".
A filtered portal with a summary field can be used with a filter expression that excludes the "exclude" records
A calculation field can be defined such as: If ( ex_name ≠ "Exclude" ; Ex_credit ) and then your sum function or summary field can compute the total(sum) of this calculation field.