File Upload Validation Using JQuery MultiFile Plugin

Question

 This is My aspx Page, where i have fileUpload Control,

 

<form id="form1" runat="server">

<div>

<asp:FileUpload ID="file_upload" class="multi" runat="server" />

<asp:Button ID="btnUpload" runat="server" Text="Upload" onclick="btnUpload_Click" /><br />

</div>

</form>

 

And I have Used "<script src="jquery.MultiFile.js" type="text/javascript"></script>" Plugin to Upload Multiple File, How can i dynamically override this Plugin to validate file Extentions