编写阶乘计算精确值的自定义函数

Function MyFact(DNumber)
Dim ArrJG, ArrTemp
Dim SumA As Double
Dim i&, j&
Dim strJG$  '结果输出
'计算阶乘长度
SumA = 1
For i = 1 To DNumber
SumA = Log(i) / Log(10) + SumA
Next i
ReDim ArrJG(Int(SumA) - 1)
ReDim ArrTemp(UBound(ArrJG))
'初始化结果数组
ArrJG(0) = 1
'计算阶乘结果
For i = 2 To DNumber
For j = 0 To UBound(ArrJG)
ArrTemp(j) = ArrJG(j) * i
Next j
j = 0
Do While j <= UBound(ArrJG)
ArrJG(j) = ArrTemp(j) Mod 10
If ArrTemp(j) >= 10 Then ArrTemp(j + 1) = ArrTemp(j + 1) + ArrTemp(j) / 10
j = j + 1
Loop
Next i
'结果输出
For i = UBound(ArrJG) To 0 Step -1
strJG = strJG & ArrJG(i)
Next i
MyFact = strJG
End Function

Sub Test()
MsgBox MyFact(100)
End Sub