here the solution
//function append mercredi
var countermercredi= 0;
var $newRow ;
$(function(){
$('#add_mer').click(function(){
countermercredi += 1;
$newRow = $('<input id="nummer' + countermercredi + '" name="nummer[]' + '" type="text" onblur="autre();" onfocus="enter();" /> ') ; $('#nummer').append($newRow)
$newRow.keypress (function (e) { return handledynmer(event, this, 'task');})
$newRow.autocomplete(autocompOpt);
$('#clientmer').append(
( '<input id="clientmer' + countermercredi + '" name="clientmer[]' + '" readonly type="text" onblur="autre();" onfocus="enter();" />')
)
$('#prodescmer').append(
( '<input id="prodescmer' + countermercredi + '" name="prodescmer[]' + '" readonly type="text" onblur="autre();" onfocus="enter();" />')
)
$('#protachemer').append(
( '<textarea id="protachemer' + countermercredi + '" name="protachemer[]' + '" type="text" rows="1" cols="20" onblur="autre();" onfocus="enter();" />')
)
$('#prolieudivmmer').append(
( '<input id="prolieudivmmer' + countermercredi + '" name="prolieudivmmer[]' + '" type="text" onblur="autre();" onfocus="enter();" />')
)
select = $('<select id="tachedivmer' + countermercredi + '" name="tachedivmer[]" type="text" onblur="autre();" onfocus="enter();" />');
select.append($("#Selectmercredi option").clone());
$("#tachedivmer").append(select);
$('#calculTempsdivmer').append(
( '<input id="calculTempsdivmer' + countermercredi + '" name="calculTempsdivmer[]' + '" type="number" size="10" min="0" max="24" value="0" class="dynamic" onblur="autre();" onfocus="enter();"/>')
)
//désactive champs précédent.
if (countermercredi > 1 )
{
countermercredi = countermercredi - 1 ;
document.getElementById('nummer'+countermercredi).readOnly = true;
countermercredi = countermercredi + 1 ;
}
});
});
//remove mercredi
$(function(){
$('#remove_mercredi').click(function(){
var calculTempsdivmer = document.getElementById("calculTempsdivmer"+countermercredi);
var tachedivmer = document.getElementById("tachedivmer"+countermercredi);
var prolieudivmmer = document.getElementById("prolieudivmmer"+countermercredi);
var protachemer = document.getElementById("protachemer"+countermercredi);
var prodescmer = document.getElementById("prodescmer"+countermercredi);
var clientmer = document.getElementById("clientmer"+countermercredi);
var nummer = document.getElementById("nummer"+countermercredi);
nummer.remove();
clientmer.remove();
prodescmer.remove();
protachemer.remove();
calculTempsdivmer.remove();
tachedivmer.remove();
prolieudivmmer.remove();
countermercredi = countermercredi - 1 ;
document.getElementById('nummer'+countermercredi).readOnly = false;
});
});