Código HTML:
... ... <td class='campo' > <form style='margin-bottom: 10px;' name='FormBorrar' method='post' action='../gabinete/form.insert.php'> <input type='hidden' name='idEvento' value='".$fila['idEvento']."'> <a href='javascript:document.FormBorrar.submit();'> <img class='ImgLista' src='../images/boton_borrar.png'> </a> </form> </td> ... ...