Amazon MWS - Signature Hashing with Access VBA


I'm having an issue get the Base64 HMAC on Amazon MWS correctly, I can get the SHA256 one to match perfectly but when I then try to convert to Base64 the result is incorrect, the code I am using to do the SHA256 part is as below

Dim lngLoop As Long
Dim oUTF, oEnc
Dim HMAC() As Byte
Dim strTemp As String
Set oUTF = CreateObject("System.Text.UTF8Encoding")
Set oEnc = CreateObject("System.Security.Cryptography.HMACSHA256")
oEnc.Key = oUTF.GetBytes_4("--------------")
HMAC = oEnc.ComputeHash_2(oUTF.GetBytes_4(StringToSign))
For lngLoop = 0 To UBound(HMAC)
     strTemp = strTemp & LCase(Right("0" & Hex(HMAC(lngLoop)), 2))

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But I believe this has be passed to the Base64 encoder as binary or a byte, but i'm having trouble converting a string in Access to a Byte? Is there an easy way to do this?

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Gustav BrockCIOCommented:
What is the output and what should it (the expected output) be?
Kbba04527Author Commented:
Hi Gustav,

I should have

SHA 256 HMAC      7b753085a5119a2ebe1ea5f0ae62097391fd1767c84ece94b9dc7a87d8c7f633
Base64 HMAC      e3UwhaURmi6+HqXwrmIJc5H9F2fITs6Uudx6h9jH9jM=

I match the SHA 256      7b753085a5119a2ebe1ea5f0ae62097391fd1767c84ece94b9dc7a87d8c7f633 but for the Base64 I get

which as a straight conversion is correct, but I think I should be feeding it in differently?

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