Equality of weight and exchange in the same gathering when selling gold for gold

A: If the jeweler will manufacture your gold upon your request, and take a wage for his work, there is no harm in this. However, if he makes you the jewelry from new gold other than your old gold, and then takes yours in return for his wage, this is impermissible. Equivalence must exist in quantity when selling gold for gold, along with mutual exchange at the same session. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.