How To Handle Enter Key On Website

When I press enter in my loginform, my search form at the top of the website runs instead. I'm trying to handle the enter key but I keep getting a missingmemberexception.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Dim getButton As New findbuttonControl
Dim vButton As Object
Dim getPassword As New findChildControl
Dim vPassword As Object
vButton = getButton.getGrandChildValue(Me.LoginView1.Controls, "Login1", "LoginButton")
vPassword = getPassword.getGrandChildValue(Me.LoginView1.Controls, "Login1", "Password")
vPassword.Attributes.Add("onkeydown", "if(event.which || event.keyCode){if ((event.which == 13) || (event.keyCode == 13)) {document.getElementById('" + vButton + "').click();return false;}} else {return true}; ")
End Sub