Option Explicit

Private Declare Function ExpandEnvironmentStringsW Lib "kernel32" ( _
   ByVal lpSrc As Long, ByVal lpDst As Long, ByVal nSize As Long) As Long

Private Function ExpandEnvironmentStrings(sSrc As String) As String
 Dim cchLen As Long
 cchLen = ExpandEnvironmentStringsW(StrPtr(sSrc),  0 ,  0 )
 If cchLen Then
    ExpandEnvironmentStrings = String$(cchLen -  1 ,  0 )
    cchLen = ExpandEnvironmentStringsW(StrPtr(sSrc), _
                                       StrPtr(ExpandEnvironmentStrings), cchLen)
 End If
End Function

Private Sub Command1_Click()
 Debug.Print ExpandEnvironmentStrings("%appdata%")
End Sub