Thank you for reaching out to us.
It is fully permissible to clean oneself for a hefsek taharah on the morning of the day on which it is planned. (We suggest attempting a bedikah then, too, to serve as a back up in case the hefsek is missed later.) An alternative would be to bring wipes or a washcloth to work and to use them to clean the vaginal area, in the bathroom.
Please get back to us with any further questions.