function create_champ(i) {

var i2 = i + 1;

document.getElementById('leschamps_'+i).innerHTML = '<input type="text" name="pays2'+i+'" > <input type="text" name="nature2'+i+'"> <input  type="text" name="duree2'+i+'"> <input type="text" name="dattes2'+i+' id=w3"> <input type="button" value="Cal"  /></span>';
document.getElementById('leschamps_'+i).innerHTML += (i <= 100) ? '<br /><span id="leschamps_'+i2+'"><a href="javascript:create_champ('+i2+')">Ajouter un champs</a></span>' : '';


}