关于超长数字的乘法计算的探讨（VBA千位以上的计算）
由于Excel的限制，其最大的有效计算位数只有12位左右，对于100位以上的精确计算，Excel自带函数/公式已无法满足要求。
小弟在此发个计算方式，希望能抛砖引玉，望各路高手共同交流讨论。
Option Base 1Option Explicit'强行求2个数的精确乘积.Function SuperProduct(Value1, Value2) As String 'VTmp: 待用的Value储存值, VLen: Value的长度, VPoint: Value的小数点位置(0=无小数点). Dim sVTmp1 As String, lVLen1 As Long, lVPoint1 As Long Dim sVTmp2 As String, lVLen2 As Long, lVPoint2 As Long 'SuperProductN的小数点位置. Dim lVPointT As Long sVTmp1 = Trim$(Value1) sVTmp2 = Trim$(Value2) SuperProduct = "0" '如果有错误，表明参数可能含有数组或对象. If Err.Number <> 0 Then Exit Function ElseIf sVTmp1 = "" Or sVTmp2 = "" Or sVTmp1 = "0" Or sVTmp2 = "0" Then Exit Function End If lVLen1 = Len(sVTmp1) lVLen2 = Len(sVTmp2) '定义各临时变量. Dim i As Long, j As Long, lGroup1 As Long, lGroup2 As Long Dim dArray1() As Double, dArray2() As Double Dim dSuperArray() As Double 'SuperProduct的临时存储变量. Dim sStmp As String '获取Value的小数点位置. lVPoint1 = 0 For i = 1 To lVLen1 If Mid$(sVTmp1, i, 1) = "." Then lVPoint1 = i Exit For End If Next i lVPoint2 = 0 For i = 1 To lVLen1 If Mid$(sVTmp2, i, 1) = "." Then lVPoint2 = i Exit For End If Next i '反馈SuperProduct的小数点位置. If lVPoint1 + lVPoint2 > 0 Then lVPointT = lVLen1 + lVLen2 - lVPoint1 - lVPoint2 Else lVPointT = 0 End If '将参数按整数处理，然后再在最终结果中插入小数点. If lVPoint1 > 0 Then sVTmp1 = Left$(sVTmp1, lVPoint1 - 1) & Right$(sVTmp1, lVLen1 - lVPoint1) End If If lVPoint2 > 0 Then sVTmp2 = Left$(sVTmp2, lVPoint2 - 1) & Right$(sVTmp2, lVLen2 - lVPoint2) End If lVLen1 = Len(sVTmp1) lVLen2 = Len(sVTmp2) '将Value按4个数字一组分别计算，若分组不足4位的，用0补齐（前端补齐）. If lVLen1 Mod 4 > 0 Then sVTmp1 = Right$("000" & sVTmp1, lVLen1 + 4 - lVLen1 Mod 4) End If If lVLen2 Mod 4 > 0 Then sVTmp2 = Right$("000" & sVTmp2, lVLen2 + 4 - lVLen2 Mod 4) End If '将Value拆成Group组，并分别存如Array中；另外再定义用于临时存储结果片段的SuperArray. lGroup1 = Len(sVTmp1) \ 4 lGroup2 = Len(sVTmp2) \ 4 ReDim dArray1(lGroup1) ReDim dArray2(lGroup2) ReDim dSuperArray(lGroup1 + lGroup2 - 1) For i = 1 To lGroup1 dArray1(i) = CDbl(Mid(sVTmp1, 4 * i - 3, 4)) Next i For i = 1 To lGroup2 dArray2(i) = CDbl(Mid(sVTmp2, 4 * i - 3, 4)) Next i '对两个Array中的片段两两相乘，并将各片段的结果储存在SuperArray中. For i = 1 To lGroup1 For j = 1 To lGroup2 dSuperArray(i + j - 1) = dArray1(i) * dArray2(j) + dSuperArray(i + j - 1) Next j Next i '将SuperArray的各片段拼贴到sStmp中. sStmp = "" For i = lGroup1 + lGroup2 - 1 To 2 Step -1 sStmp = Right$("0000" & CStr(dSuperArray(i)), 4) & sStmp dSuperArray(i - 1) = dSuperArray(i - 1) + CDbl(Left$("0000" & CStr(dSuperArray(i)), Len(CStr(dSuperArray(i))))) Next i sStmp = CStr(dSuperArray(1)) & sStmp '补入小数点. If lVPointT > 0 Then SuperProduct = Left$(sStmp, Len(sStmp) - lVPointT) & "." & Right$(sStmp, lVPointT) Else SuperProduct = sStmp End If '释放内存. sVTmp1 = "" sVTmp2 = "" sStmp = "" Erase dArray1 Erase dArray2 Erase dSuperArray End Function