problem in loading UserControl from code behind.

Used the following code to load usercontrol.
App_UserControls_GenEmployment genEm = (App_UserControls_GenEmployment)Page.LoadControl("~/App_UserControls/GenEmployment.ascx")
I have created a fileupload control with onchange event inside that usercontrol already. but that is not called. throwing FileSelectGenEmp undefined error in javascript. but i have created that Function inside that usercontrol.
<input type="file" runat="server" id="fupEmployment" onchange="FileSelectGenEmp(this.id)" multiple="multiple" />