//Get the New Supplier Account Selected before save
const supplierAccountName = value;
//Get the Supplier Contact Field Object
const supplierContactField = ZDK.Page.getField('Supplier_Contact');
//Check the Supplier Account Field is not empty
if (supplierAccountName) {
    //Add criteria to filter the lookup field
    supplierContactField.setCriteria("(Account_Name:equals:" + supplierAccountName + ")", {filterOnSearch: true});
}