Praise be to Allah.
If the jeweller is going to make your gold into jewellery, as you have asked him to, and then take a fee for his work, there is nothing wrong with that. But if he is going to make the jewellery from gold that is not yours, and he will take your gold as payment in addition to his fee, this is not permissible, because when gold is sold in exchange for gold, the amounts must be equal, and the transaction must be completed in one sitting.
And Allaah is the Source of strength. May Allaah bless our Prophet Muhammad and his family and companions, and grant them peace.