How to specify exactly the last time webViewDidFinishLoad for UIWebView get called?

I've read the previous post for this question, UIWebView - How to identify the “last” webViewDidFinishLoad message? but in fact I didn't get the answer very much. what I need is to execute a script on the webView but after it finishes its loading completely. I've tried to count the frames inside the HTML by reading it to a string and then counting them then loading the string I've read to the UIWebView, and 开发者_StackOverflow社区counting the times webViewDidFinishLoad gets called but that's didn't work. so is there a way to accomplish that, or can any body tell me when webViewDidFinishLoad gets called exactly so I can count something and use it instead of the frames.

thank you in advance.