Does a divorce occur with the oath, "My wife is divorced if [the worker] works in any of the establishments, for I will not work there," if the worker returns to work, knowing that the intention was never to work with him again, and that the questioner is still in the period of the marriage contract?

If you did not intend immediacy in your oath, and you did not break it, then waiting for the worker for a short period does not constitute a breach. If you intended by your oath never to work with this worker, and the worker arrived while you remained at work, your divorce takes effect and your wife becomes irrevocably divorced from you, as long as you have not consummated the marriage with her. This is the view of the majority of scholars. However, if you swore an oath with the intention of emphasis and threat, and not with the intention of effecting a divorce, then if you break it, your divorce does not take effect, but you are liable for an expiation for an oath. The lawful oath is to swear by Allah the Almighty, whereas swearing by divorce is among the oaths of the dissolute.