run javascript function on griview pageindexchanging event

I have a gridview, with paging enabled. This is the link when I want to go to second page

<a href="javascript:__doPostBack('ctl00$ContentPlaceHolder1$gv','Page$2')">

The problem is that I require to run the CheckValid() function before paging is done - user cannot page with invalid details. How can I set the HREF to allow this?

<a href= "if Checkvalid() then "javascript:__doPostBack('ctl00$ContentPlaceHolder1$gv','Page$2')"">

google doesn't return any answers I could find

In your case, pagers are generated by ASP.NET, so you can't do much server-side. You have to run a client-side script which, in steps: 1-Finds the pager anchors 2-replace (and store) their href with an onclick function 3-create your validation function that, if successfull, calls the original stored function "__doPostBack".

That's not so complicated if you get the help of client-side tools like Firebug or Chrome developer tools.