function filterThrough(pFilter) {
    var inp1 = document.createElement("INPUT");
    inp1.setAttribute("TYPE", "hidden");
    inp1.setAttribute("NAME", "provider_filter");
    inp1.setAttribute("VALUE", pFilter);
    
    document.forms.main_form.appendChild(inp1); 
    document.forms.main_form.submit();
    
    return true;
}