What do you mean when you say a separate string value, can you expand on it a bit?
hope this will helps
kindly mark this answer as correct or helpful so that it will help others
Like parameter = "All" then string
parameter = [field] then field
Unfortunately I tried that and it fails on the basis of not having a null value to exclude
I'm probably complicating this more than I need to I will be back with the results thank you