您好，以下是原創示例，供您參考：
Dear Manager Williams,
Thank you for your invitation for attending your company's 5th anniversary celebration. Unfortunately, urgent matters that I will be on business in another city. Hope you understand the reasons preventing my attendance.
Thank you for the invitation again and hop our long-term cooperation go smoothly and closely.
Yours Sincerely,
xxx
回復商業邀請重在簡單明了，言語嚴謹。壹句話解釋為什麽不能去，最後或者祝福活動順利或者祝福合作愉快。落款yours sincerely, 標準名字即可。
希望有所幫助，謝謝！