How to change attribute requirepment level permanently ?

Hi,

when I changing required level for a field, it works only when form is open. When I reopen a form, required level returns to default.  How can I change level permanently ?

this is part of my code

        if (prospectText == valueToTrigger) {
            Xrm.Page.data.entity.attributes.get(attributeToChange).setRequiredLevel("required");
        }
        else {
            Xrm.Page.data.entity.attributes.get(attributeToChange).setRequiredLevel("none");
        }
        Xrm.Page.data.entity.attributes.get(attributeToChange).setSubmitMode("always");