It sounds like you want to exclude all documents that have a status of 90 and a blank closed date. The best way to do this is write a formula to show only those documents, then reverse the logic by placing it in a NOT expression.
To show only those documents:
SELECT Status = 90 & DateS90 = “”
To show all documents that do not meet that condition:
SELECT !(Status = 90 & DateS90 = “”)
This will work in all versions of Notes.