用VB编写一个将n进制整数转换成十进制数的通用程序！

重点是要学会如何利用按权展开式求和，算法了解了，代码就不难了。

Dim a As String, aa As Integer, b As String, bb As Integer, c As Integer
aa = InputBox("输入的是几进制数？")
aa = Trim(aa)
a = InputBox("数是多少？")
a = Trim(a)
For i = 1 To Len(a)
    b = Mid(a, i, 1)
    If (b > 9) Then
        bb = 10 + b - Asc("A")
    Else
        bb = Val(b)
    End If
                                                                    
    c = c + bb * aa ^ (Len(a) - i)
Next i
MsgBox "结果是：" & c