In asp.net - you can only have ONE <form on a a page.
And that form is created by the DNN Framework.

So for starters you need to remove the <form action=  statement.

Secondly - unless you want to try manually messing around with Javascript tricks.
You should base your markup on <asp: based controls.

The <asp:Button control handles the processing of a BUTTON on a page and
the javascript needed to get the click action hadded back to your page code.

<asp:Button ID="cmdSEARCH" runat="server" Text="SEARCH" />

You then add code to your module's .vb code behind/beside file that handles the CLICK event:

 Protected Sub cmdSEARCH_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSEARCH.Click   
     'Any code you want here
   
    Response.Redirect("cint_portal/LinkClick.aspx?link=54&amp;tabid=36", True)

End Sub