You have a full-time job and are also doing a part-time evening course. You now find that you cannot continue the course. Write a letter to the course tutor. In your letter
Describe the situation
Explain why you cannot continue at this time
Say what action you would like to take
Dear Mr. Smith,
I am writing to inform you that I will be unable to continue with the part-time computer programing course.
I have been attending your evening classes for the last two months, and have enjoyed them immensely. As I stated on my course application form, I work full-time for a large IT company, and until now I have managed to fit the programing course into my schedule.
However, my company is currently on the verge of signing a contract with an important new client in China, and I am part of the team that is being sent to Beijing to negotiate terms and conditions. I will probably be out of the country for several weeks.
I am aware that you run the same course twice a year. Rather than try to catch up when I return from China, I was wondering if it would be possible for me to join the next cohort in September.
I look forward to receiving your response.