I'm trying to find the fastest way to do this. I've written a function where you input a string of numbers and it takes the first 2 characters and repeats them until the new string has the same length of the input string.

So input = 56378, output = 56565. Input=89432, output=89898

This is what I have now:
Code:
Private Function Alternate(Num As String) As String
Dim first(0 To 1) As String, x As Long
    first(1) = Mid$(Num, 1, 1)
    first(0) = Mid$(Num, 2, 1)
    For x = 1 To Len(Num)
        Alternate = Alternate & first(x Mod 2)
    Next x
End Function
Can you guys think of anything faster?