DynamoDB ProjectionExpression exclude attribute (all fields except one)

I have a requirement where my dynamodb table has many attributes, and i need all of them in the projection expression except one or two columns which i dont need in response. (I am scanning the table).
Is there a way how can i define this in ProjectionExpression (all except this one column).
I have seen examples where ProjectionExpression only takes what all "is required" and not the other way.