请教，下面这段程序，最大只能将“7FFFFFFF”转换成十进制，再大就报溢出错误了，我猜想，这是Long的限制，因为Long最大也就是到“7FFFFFFF”，但计算机自带的计算器则并没有这个现象，可达到“7FFFFFFFFFFFFFFF”，它是怎样计算的呢？求能突破“7FFFFFFF”限制的方法，谢谢！

Private Sub Command1_Click()
    Print HEX_to_DEC("80000000")
End Sub

Public Function HEX_to_DEC(ByVal Hex As String) As Long
    Dim i As Long
    Dim b As Long
    
    Hex = UCase(Hex)
    For i = 1 To Len(Hex)
        Select Case Mid(Hex, Len(Hex) - i + 1, 1)
        Case "0": b = b + 16 ^ (i - 1) * 0
        Case "1": b = b + 16 ^ (i - 1) * 1
        Case "2": b = b + 16 ^ (i - 1) * 2
        Case "3": b = b + 16 ^ (i - 1) * 3
        Case "4": b = b + 16 ^ (i - 1) * 4
        Case "5": b = b + 16 ^ (i - 1) * 5
        Case "6": b = b + 16 ^ (i - 1) * 6
        Case "7": b = b + 16 ^ (i - 1) * 7
        Case "8": b = b + 16 ^ (i - 1) * 8
        Case "9": b = b + 16 ^ (i - 1) * 9
        Case "A": b = b + 16 ^ (i - 1) * 10
        Case "B": b = b + 16 ^ (i - 1) * 11
        Case "C": b = b + 16 ^ (i - 1) * 12
        Case "D": b = b + 16 ^ (i - 1) * 13
        Case "E": b = b + 16 ^ (i - 1) * 14
        Case "F": b = b + 16 ^ (i - 1) * 15
        End Select
    Next i
    HEX_to_DEC = b
End Function

能麻烦版主大大给个例子吗？