I'm guessing your error is being caused by the disabled inputs. When you create a number type , disabled input, roll20 treats it as a calculation, so it is trying to convert the data in your hidden inputs into a number. I'm not 100% sure, but that would be my guess. You can change your inputs from this: <input type="hidden" name="attr_foo_competence1" value="0" /> <input type="text" name="attr_competence1" value="@{foo_competence1}" disabled="true"/> to this: <input type="text" name="attr_competence1" value="--" readonly /> The hidden input isn't necessary. Your sheet worker looks structurally okay, except for the setAttrs. It's always best to use a single setAttrs function, so instead of this: setAttrs({ foo_competence1: competence1 }); setAttrs({ foo_competence2: competence2 }); setAttrs({ foo_competence3_1: competence3_1 }); setAttrs({ foo_competence3_2: competence3_2 }); setAttrs({ foo_competence4_1: competence4_1 }); setAttrs({ foo_competence4_2: competence4_2 }); setAttrs({ foo_competence4_3: competence4_3 }); Try this: setAttrs({ foo_competence1: competence1, foo_competence2: competence2, foo_competence3_1: competence3_1, foo_competence3_2: competence3_2, foo_competence4_1: competence4_1, foo_competence4_2: competence4_2, foo_competence4_3: competence4_3 }); But you can do something simpler, since your data is already stored in the format that setAttrs needs, you can do this (untested): <script type="text/worker"> const characterData = { "Ann": { "competence1" : "Soif de sang : Mêlée", "competence2" : "Une action en plus", "competence3_1" : "Une action de Magie gratuite en plus", "competence3_2" : "Une action de Mêlée gratuite en plus", "competence4_1" : "Une action de Combat gratuite en plus", "competence4_2" : "1points ajouté au résultat du dé de Combat", "competence4_3" : "Sur un 6 : +1 au dé de Combat" }, "Arnaud" : { "competence1" : "Une action de Fouille gratuite en plus", "competence2" : "Une action en plus", "competence3_1" : "Un dé de Mêlée en plus", "competence3_2" : "Une action de Déplacement gratuite en plus", "competence4_1" : "+1 erg'", "competence4_2" : "reg", "competence4_3" : "ergerg" } }; on("sheet:opened change:nom_personnage", function() { getAttrs(["nom_personnage"], function(value) { let competence = { "competence1" : "--", "competence2" : "--", "competence3_1" : "--", "competence3_2" : "--", "competence4_1" : "--", "competence4_2" : "--", "competence4_3" : "--" } if (value.nom_personnage in characterData) { console.log("Mise en place des paramètres de '" + value.nom_personnage + "'"); competence = characterData[value.nom_personnage]; } else { console.log("Mise en place des paramètres vides"); } setAttrs(competence); }); }); </script>