Sub Foo()

    Dim str As String

    str = "Hello"

    Bar (str)
    Debug.Print str 'prints "Hello" because str is evaluated and a copy is passed

    Bar str 'or Call Bar(str)
    Debug.Print str 'prints "Hello World"

End Sub

Sub Bar(ByRef param As String)

    param = param + " World"

End Sub

Sub Test()
Dim str As String
str = "Cannot be replaced if passed ByVal"

' The following call passes str ByVal even though it is declared ByRef.
Call setNewString((str))
' The parentheses around str protect it from change.
MsgBox (str)

' The following call allows str to be passed ByRef as declared.
Call setNewString(str)
' Variable str is not protected from change.
MsgBox (str)
End Sub

Sub setNewString(ByRef inString As String)
    inString = "This is a new value for the inString argument."
    MsgBox (inString)
End Sub