Public Function OEMConvert(ByRef Text As String, ByVal FromAscii As Boolean) As String
    Static OInit   As Boolean
    Static Os(255) As Byte 'Ascii
    Static Oc(255) As Byte 'Ansi
    Dim t()        As Byte
    Dim i          As Long
    
    If Not OInit Then
        For i = 0 To 255
            Os(i) = i: Oc(i) = i
        Next
        Os(132) = 228: Os(148) = 246: Os(129) = 252: Os(225) = 223: Os(142) = 196: Os(153) = 214: Os(154) = 220: Os(128) = 199
        Os(130) = 233: Os(131) = 226: Os(133) = 224: Os(134) = 229: Os(135) = 231: Os(136) = 234: Os(137) = 235: Os(138) = 232
        Os(139) = 239: Os(140) = 238: Os(143) = 197: Os(144) = 201: Os(147) = 244: Os(150) = 251: Os(151) = 249: Os(20) = 182
        Os(145) = 230: Os(146) = 198: Os(155) = 162: Os(156) = 163: Os(166) = 170: Os(167) = 186: Os(171) = 189: Os(172) = 188
        Os(237) = 216: Os(241) = 177: Os(246) = 247: Os(253) = 178: Os(21) = 167:  Os(157) = 165
        Oc(228) = 132: Oc(246) = 148: Oc(252) = 129: Oc(223) = 225: Oc(196) = 142: Oc(214) = 153: Oc(220) = 154: Oc(199) = 128
        Oc(233) = 130: Oc(226) = 131: Oc(224) = 133: Oc(229) = 134: Oc(231) = 135: Oc(234) = 136: Oc(235) = 137: Oc(232) = 138
        Oc(239) = 139: Oc(238) = 140: Oc(197) = 143: Oc(201) = 144: Oc(244) = 147: Oc(251) = 150: Oc(249) = 151: Oc(182) = 20:
        Oc(230) = 145: Oc(198) = 146: Oc(162) = 155: Oc(163) = 156: Oc(170) = 166: Oc(186) = 167: Oc(189) = 171: Oc(188) = 172:
        Oc(216) = 237: Oc(177) = 241: Oc(247) = 246: Oc(178) = 253: Oc(167) = 21:  Oc(165) = 157
        OInit = True
    End If
    
    If (Len(Text) = 0) Then Exit Function
    
    t = StrConv(Text, vbFromUnicode)
    If FromAscii Then
        For i = 0 To UBound(t)
            t(i) = Os(t(i))
        Next
    Else
        For i = 0 To UBound(t)
            t(i) = Oc(t(i))
        Next
    End If
    OEMConvert = StrConv(t, vbUnicode)
    
End Function

AnsiVersOEM(ChaineAconvertir)
OemVersAnsi(ChaineAconvertir)

Private Declare Function CharToOem Lib "user32" Alias "CharToOemA" (ByVal lpszSrc As String, ByVal lpszDst As String) As Long
Private Declare Function OemToChar Lib "user32" Alias "OemToCharA" (ByVal lpszSrc As String, ByVal lpszDst As String) As Long

Public Sub Main()
    Debug.Print "From ANSI  : " & OEMConvert("éèà", False)
    Debug.Print "From ASCII : " & OEMConvert("‚Š…", True)
End Sub

Public Function OEMConvert(ByRef Text As String, ByVal FromAscii As Boolean) As String
    OEMConvert = Text
    If FromAscii Then
        OemToChar OEMConvert, OEMConvert
    Else
        CharToOem OEMConvert, OEMConvert
    End If
End Function

Declare Function OemToCharBuff Lib "user32" Alias "OemToCharBuffA" (ByVal lpszSrc As String, ByVal lpszDst As String, ByVal cchDstLength As Integer) As Integer
Declare Function CharToOemBuff Lib "user32" Alias "CharToOemBuffA" (ByVal lpszSrc As String, ByVal lpszDst As String, ByVal cchDstLength As Integer) As Integer
    Function ASCIItoANSI(ByVal Text As String) As String
        Dim strRet As String = New String("  ", Text.Length)
        OemToCharBuff(Text, strRet, Text.Length)
        Return strRet
    End Function
    Function ANSItoASCII(ByVal Text As String) As String
        Dim strRet As String = New String(" ", Text.Length)
        CharToOemBuff(Text, strRet, Text.Length)
        Return strRet
    End Function

'    EXEMPLE  D'UTILISATION
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As  System.EventArgs) Handles MyBase.Load
        Dim strValue1 As String = "€"
        Dim strValue2 As String = "Ç"
        MessageBox.Show(strValue1 & "  ->  " & ASCIItoANSI(strvalue1))
        MessageBox.Show(strValue2 & "  ->  " & ANSItoASCII(strValue2))
    End Sub