Public Declare Function fnl Lib "dllname" (Byval Out As String, Byval In1 As String, Byval In1Len As Long, Byval In2 As String, Byval In2Len As Long) As Long
or
Public Declare Function fnl Lib "dllname" (Out() As Byte, In1() As Byte, Byval In1Len As Long, In2() As Byte, Byval In2Len As Long) As Long