If you forget b’ones to daven Mincha you may daven Shmoneh Esrei by Maariv twice. Rav Ephraim Greenblatt in Rivevos Ephraim (1:166) says that the Acharonim hold that even if you are in middle of a business deal and you will lose money of you stop to daven, that is also considered an Ones and you may continue your dealings and daven Shmoneh Esrei by Maariv twice. Moreover says Rav Greenblatt even if you will not lose money only profit, it is still considered an Ones.
However asks Rav Greenblatt, what happens if you had the whole afternoon to daven but decided to wait for later. Only when later came you found yourself caught up in business. Is that also considered an Ones? Even in this case he says that you are an Ones. The fact that you did not daven earlier does not make you negligent since you had every reason to believe you will daven later. Not that you became busy you are considered an Ones.
In order not to face this situation, the Rivevos Ephraim suggests to schedule yourself to daven an early Mincha leaving plenty of time in case of emergency business concerns.