ReferenceError: formContext is not defined

I have this error when I want to add a record to the form of my dynamics 365 and this is what I have in the script

function VisibleRiskLevelField(executionContext) {
    var formContext = executionContext.getFormContext();
    if (formContext.getAttribute("axn_shephaseii").getValue() != null ) {
        formContext.getControl("axn_risklevel").setVisible(false);
        formContext.getAttribute("axn_risklevel").setRequiredLevel("none");
    }else {
         DisabledField();
   }
}