以下代码如何修改,才能限制上传文件类型?

<%
Dim FormData, FormSize, Divider, bCrLf
FormSize = Request.TotalBytes
FormData = Request.BinaryRead(FormSize)
bCrLf = ChrB(13) & ChrB(10)
Divider = LeftB(FormData, InStrB(FormData, bCrLf) - 1)
Function SaveFile(FormFileField, Path, MaxSize, SavType)
Dim StreamObj,StreamObj1
Set StreamObj = Server.CreateObject("ADODB.Stream")
Set StreamObj1 = Server.CreateObject("ADODB.Stream")
StreamObj.Mode = 3
StreamObj1.Mode = 3
StreamObj.Type = 1
StreamObj1.Type = 1
SaveFile = ""
StartPos = LenB(Divider) + 2
FormFileField = Chr(34) & FormFileField & Chr(34)
If Right(Path,1) <> "" Then
Path = Path & ""
End If
Do While StartPos > 0
strlen = InStrB(StartPos, FormData, bCrLf) - StartPos
SearchStr = MidB(FormData, StartPos, strlen)
If InStr(bin2str(SearchStr), FormFileField) > 0 Then
FileName = bin2str(GetFileName(SearchStr,path,SavType))
If FileName <> "" Then
FileStart = InStrB(StartPos, FormData, bCrLf & bCrLf) + 4
FileLen = InStrB(StartPos, FormData, Divider) - 2 - FileStart
If FileLen <= MaxSize*1024 Then
FileContent = MidB(FormData, FileStart, FileLen)
StreamObj.Open
StreamObj1.Open
StreamObj.Write FormData
StreamObj.Position=FileStart-1
StreamObj.CopyTo StreamObj1,FileLen
If SavType =0 Then
SavType = 1
End If
StreamObj1.SaveToFile Path & FileName, SavType
StreamObj.Close
StreamObj1.Close
If SaveFile <> "" Then
SaveFile = SaveFile & "," & FileName
Else
SaveFile = FileName '显示出的文件名
End If
Else
If SaveFile <> "" Then
SaveFile = SaveFile & ",*TooBig*"
Else
SaveFile = "*TooBig*"
End If
End If
End If
End If
If InStrB(StartPos, FormData, Divider) < 1 Then