Да забыл. Если кому интересно получилось так:

В модуле обявляем функцию
Public Declare Function OwenIOUniversal Lib "owen_io" Alias "OwenIO" _
(ByVal adr As Integer, _
ByVal adr_type As Integer, _
ByVal is_read As Integer, _
ByVal command As String, _
ByVal params As String, _
ByRef param_sz As Integer) As Integer

Вызываем
Dim arr(0) As Byte
Dim res As Integer = OwenIOUniversal(mvarDevAdr, 0, 0, "INIT", arr(0), 0)