Sub Main
    Call ModifyField()   
End Sub


Function ModifyField
    Set db = Client.OpenDatabase("myfile.IMD")
    Set task = db.TableManagement
    Set field = db.TableDef.NewField
    field.Name = "newname"
    field.Description = "field"
    field.Type = WI_CHAR_FIELD
    field.Equation = ""
    field.Length = 1
    task.ReplaceField "oldname", field
    task.PerformTask
    Set task = Nothing
    Set db = Nothing
    Set field = Nothing
End Function