Create Field in Access DB

I am currenty using:

Code:

---

    Dim dbs As Database
    Dim f As Field

    Set dbs = OpenDatabase(App.Path & "\Database\SIS.mdb")
    Set f = dbs.TableDefs("USER").CreateField("Shipment_NextDate", dbDate, 10)

    dbs.TableDefs("USER").Fields.Append f
    dbs.Close
    Set dbs = Nothing

---

Error = Type Mismatch


Any ideas?

VB Code:

Set f = dbs.TableDefs("USER").CreateField("Shipment_NextDate", dbDate)

if not.. what line does the error occur?