看了二十四画生的Blog的大小写金额转换函数，自己也对照着写了个VB.NET的，然后用类封装了一下。
原版C#版的，可以看原作者的代码。

    Public Class Currency
        Inherits Object
 
        Private Const CST_CAPSTR_TAIL As String = "整"
        Private Const CST_CAPSSTR_ZERO As String = "零"
        Private Const CST_CAPSSTR As String = CST_CAPSSTR_ZERO & "壹贰叁肆伍陆柒捌玖"
        Private Const CST_POSSTR_YUAN As String = "元"
        Private Const CST_POSSTR As String = "万仟佰拾亿仟佰拾万仟佰拾" & CST_POSSTR_YUAN & "角分"
        Private Const CST_CHNNUM_ZERO As String = CST_CAPSSTR_ZERO & CST_POSSTR_YUAN & CST_CAPSTR_TAIL
 
        Private Shared ReadOnly CST_MAXLENGTH As Integer = CST_POSSTR.Length
 
        Public Shared Function ConvertToCapsString(ByVal dec As Decimal) As String
            Dim i, j, nZero As Integer
            Dim strDec, strPos, ch1, ch2 As String
            Dim chnNum, chnPos As String
            Dim strOnePosValue As String
            Dim intOnePosValue As Integer
 
            '将num取绝对值并四舍五入取2位小数
            dec = Math.Round(Math.Abs(dec), 2)
            '将num乘100并转换成字符串形式
            strDec = Convert.ToInt64(dec * 100).ToString
            '找出最高位
            j = strDec.Length
            If i > CST_MAXLENGTH Then
                Throw New OverflowException
            ElseIf dec = 0 Then
                '零元的时候，直接输出“零元整”
                chnNum = CST_CHNNUM_ZERO
            Else
                '取出对应位数的str2的值。如：200.55,j为5所以str2=佰拾元角分
                strPos = CST_POSSTR.Substring(CST_MAXLENGTH - j)
                '循环取出每一位需要转换的值
                For i = 0 To j - 1
                    '取出需转换的某一位的值
                    strOnePosValue = strDec.Substring(i, 1)
                    '转换为数字
                    intOnePosValue = Convert.ToInt32(strOnePosValue)
                    If i <> j - 3 AndAlso i <> j - 7 AndAlso i <> j - 15 Then
                        '当所取位数不为元、万、亿、万亿上的数字时
                        If strOnePosValue = "0" Then
                            '此位为零，只计入零的个数。不转换。
                            ch1 = ""
                            ch2 = ""
                            nZero = nZero + 1
                        Else
                            '此位非零
                            If nZero = 0 Then
                                   '前面没有零，追加此位的中文
                                   ch1 = CST_CAPSSTR.Substring(intOnePosValue * 1, 1)
                                   ch2 = strPos.Substring(i, 1)
                                   nZero = 0
                            Else
                                   '前面已经有零，无论有多少只加一个零，然后追加此位的中文
                                   ch1 = CST_CAPSSTR_ZERO & CST_CAPSSTR.Substring(intOnePosValue * 1, 1)
                                   ch2 = strPos.Substring(i, 1)
                                   nZero = 0
                            End If
                        End If
                    Else
                        '该位是万亿，亿，万，元位等关键位
                        If strOnePosValue <> "0" AndAlso nZero <> 0 Then
                            ch1 = CST_CAPSSTR_ZERO & CST_CAPSSTR.Substring(intOnePosValue * 1, 1)
                            ch2 = strPos.Substring(i, 1)
                            nZero = 0
                        Else
                            If strOnePosValue <> "0" AndAlso nZero = 0 Then
                                   ch1 = CST_CAPSSTR.Substring(intOnePosValue * 1, 1)
                                   ch2 = strPos.Substring(i, 1)
                                   nZero = 0
                            Else
                                   If strOnePosValue = "0" AndAlso nZero >= 3 Then
                                       ch1 = ""
                                       ch2 = ""
                                       nZero = nZero + 1
                                   Else
                                       If j > 11 Then
                                           '亿以上
                                           ch1 = ""
                                           nZero = nZero + 1
                                       Else
                                           '亿以下
                                           ch1 = ""
                                           ch2 = strPos.Substring(i, 1)
                                           nZero = nZero + 1
                                       End If
                                   End If
                            End If
                        End If
                    End If
                    If i = j - 11 OrElse i = j - 3 Then
                        '如果该位是亿位或元位，则必须写上
                        ch2 = strPos.Substring(i, 1)
                    End If
                    chnNum = chnNum & ch1 & ch2
                    If i = j - 1 AndAlso strOnePosValue = "0" Then
                        '最后一位（分）为0时，加上“整”
                        chnNum = chnNum & CST_CAPSTR_TAIL
                    End If
                Next
            End If
            Return chnNum
        End Function
 
        Public Shared Function ConvertToCapsString(ByVal dec As String) As String
            Dim num As Decimal = 0
            Try
                num = Convert.ToDecimal(dec)
            Catch ex As Exception
                Throw New InvalidateDecimalFormatException(dec)
            End Try
            Return ConvertToCapsString(num)
        End Function
 
        Public Class OverflowException
            Inherits Exception
 
            Public Sub New()
                MyBase.New("Overflow in parameter. To string length must less than " & CST_MAXLENGTH & ".")
            End Sub
 
        End Class
 
        Public Class InvalidateDecimalFormatException
            Inherits Exception
 
            Private m_val As String
 
            Public ReadOnly Property Value() As String
                Get
                    Return m_val
                End Get
            End Property
 
            Public Sub New(ByVal val As String)
                MyBase.New("The string value cannot be converted to decimal.")
                m_val = val
            End Sub
 
        End Class
 
    End Class


出处：https://www.cnblogs.com/farrio/archive/2005/03/30/128582.html