nz did not work
Sorry, following suggession did not work.
FullName: Nz([BillingContactSalutation] & " ", "") & Nz([BillingContactFirstName] & " ", "") & Nz([BillingContactMiddleInitial] & " ", "") & Nz([BillingContactLastName])
Result
record1: mr john s edwards (works fine)
record2: mrs...