'в модуль.
Option Explicit

Enum idCodePage
    Win =  1251 
    Dos =  866 
    Koi =  20866 
    Iso =  28595 
End Enum

Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, _
        ByVal lpMultiByteStr As String, ByVal cchMultiByte As Long, ByVal lpWideCharStr As Long, _
        ByVal cchWideChar As Long) As Long
Declare Function WideCharToMultiByte Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, _
        ByVal lpWideCharStr As Long, ByVal cchWideChar As Long, ByVal lpMultiByteStr As String, _
        ByVal cchMultiByte As Long, ByVal lpDefaultChar As String, ByVal lpUsedDefaultChar As Long) As Long

Public Function ConvertCodePage(SourseString As String, inPage As idCodePage, outPage As idCodePage) As String
  Dim LenSourseString As Long
  Dim strFirst As String
  Dim strSecond As String
  Dim RetStrLong As Long
  LenSourseString = Len(SourseString)
  strFirst = String(LenSourseString *  2 , Chr( 0 ))
  strSecond = String(LenSourseString *  2 , Chr( 0 ))
  RetStrLong = MultiByteToWideChar(inPage, &H1, SourseString, LenSourseString, StrPtr(strFirst), LenSourseString)
  RetStrLong = WideCharToMultiByte(outPage,  0 , StrPtr(strFirst), RetStrLong, strSecond, LenSourseString *  2 , ByVal  0 ,  0 )
  ConvertCodePage = Left(strSecond, RetStrLong)
End Function