如果你的朋友tom前几天邀请你去参加他的生日聚会,但是你有事不能去，写英语作文

I am so glad and grateful that you have invited me to your party. But I am so sorry that I can't attend. Because my friend Tom has been ill. He can't move by himself at all and stay on bed all night. It seems that he got serious fever. So I must take him to the hospital and I can't attend your party tonight.
Happy birthday to you my dear friend. I’m so sorry that I can't accompany with you in this special day. I hope you could understand me and enjoy the party.

我可以帮你，但你总得告诉我具体写些什么内容，还有大概的字数。