Displaying a 6 digit number as 4 text characters

Recently I had to link up 2 systems, one financial off the shelf package and a bespoke Access database used for contact management.
The contact management data was going to create and maintain customer accounts in the financial package. The problem was in the access DB each contact had a unique number and in the financial package we needed a reference where the first 2 letters of the customers surname were followed with up to 4 more characters for a unique reference.
Tricky.
In the end I put together this short bit of code that allows you to convert a number to any base. All you have to do is supply the digits to use.
In my case I've used base 33 to pack the id numbers into a shorter format using numbers and letters.

Const vbB2Digits = "01" 'base 2 - Binary
Const vbB8Digits = "01234567" 'base 8 - Octal
Const vbB10Digits = "0123456789" 'base 10 - Decimal
Const vbB10Digits = "0123456789XE" 'base 12 - Dozenal. See http://www.dozenal.org
Const vbB16Digits = "0123456789ABCDEF" 'base 16 - Hexedecimal
Const vbB33Digits = "0123456789ABCDEFGHJKMNPQRSTUVWXYZ" 'base 33 - non similar characters (I,L,O removed) from 0-9 & Alphabet


Public Function sEncodeNumber(lNumber As Long, Optional sDigitList As String = vbB10Digits) As String
Dim sOutputString As String
Dim lTmpNumber As Long
Dim lRangeSize As Long
Dim lTmpPower As Long
Dim lTmpLastPower As Long

    OutputString = ""
    lTmpNumber = lNumber
    lRangeSize = Len(sDigitList)
    lTmpPower = 1

    ' Work with postive numbers
    If lTmpNumber < 0 Then
        lTmpNumber = lTmpNumber * -1
    End If

    While lTmpNumber > 0
        lTmpLastPower = lTmpPower
        lTmpPower = lTmpPower * lRangeSize
        sOutputString = Mid(sDigitList, ((lTmpNumber Mod lTmpPower) / lTmpLastPower) + 1, 1) & sOutputString
        lTmpNumber = lTmpNumber - (lTmpNumber Mod lTmpPower)
    Wend

    ' insert the -ve sign if the orginal number was negative
    If lNumber < 0 Then
        sOutputString = "-" & sOutputString
    End If

    sEncodeNumber = sOutputString
End Function

For those maths geeks out there, if you haven't come across dozenal before, have a quick gander at Alex Bellos' blog entires on the subject.