ASP中只有UrlEncode，没有Urldecode问题的解决方法？

Function URLDecode(enStr)          'URL解碼函數 
 dim deStr 
 dim c,i,v 
 deStr="" 
 for i=1 to len(enStr) 
   c=Mid(enStr,i,1) 
   if c="%" then 
     v=eval("h"+Mid(enStr,i+1,2)) 
     if v128 then 
       deStr=deStrchr(v) 
       i=i+2 
     else 
       if isvalidhex(mid(enstr,i,3)) then 
         if isvalidhex(mid(enstr,i+3,3)) then 
           v=eval("h"+Mid(enStr,i+1,2)+Mid(enStr,i+4,2)) 
           deStr=deStrchr(v) 
           i=i+5 
         else 
           v=eval("h"+Mid(enStr,i+1,2)+cstr(hex(asc(Mid(enStr,i+3,1))))) 
           deStr=deStrchr(v) 
           i=i+3 
         end if 
       else 
         destr=destrc 
       end if 
     end if 
   else 
     if c="+" then 
       deStr=deStr" " 
     else 
       deStr=deStrc 
     end if 
   end if 
 next 
 URLDecode=deStr 
end function 
 
function isvalidhex(str) 
 isvalidhex=true 
 str=ucase(str) 
 if len(str)>3 then isvalidhex=false:exit function 
 if left(str,1)>"%" then isvalidhex=false:exit function 
 c=mid(str,2,1) 
 if not (((c>="0") and (c="9")) or ((c>="A") and (c="Z"))) then isvalidhex=false:exit function 
 c=mid(str,3,1) 
 if not (((c>="0") and (c="9")) or ((c>="A") and (c="Z"))) then isvalidhex=false:exit function 
end function