If you are going to come to the party,please let me know in advance?

If you are going to (如果你計劃) come to the party(來叁加這個舞會),please (請) let me know in advance(預先讓我知道)?

華文譯：如果你要來參加派對，請讓我事先知道。(好嗎？)
# ((be going to do))（◆在((會話))， (1)也有轉換為"be gonna［gɔ`ːnə，gənə］do "的用語。(2)也有使用"be going to go [come]"。）
(釋義1)((表示未来・予定・意志))
例. He is going to write.
例. Their daughter is going to be a doctor.（◆Their daughter was going ...）
例. What are you going to do with it?
(釋義2)(3)：省略。

如果你是要來這派對，請預早通知我。

If you are going to come to the party,please let me know in advance.
如果本句的意思是"你要來派對前，請先讓我知道"，"要來派對"是雙方事先已決定好，都知道的事，則本句應修正為
When you are going to come to the party , please let me know in advance. If 改為When.

如果本句的意思是"假如你決定來參加派對，請先讓我知"，則本句應改為
If you will join the party, please let me know in advance.
或If you will come to the party, please let me know in advance.

基本上，be going to 將去做某事，文意上較傾向單純地表示未來的動作，而will 則是具較強的自主意願的字義，如本句的原意是第二個意思，使用will來表達"意願"，文意會較清楚(不會讓人感覺只是在講未來的動作）。

而如果本句的意思是第二個文意，本句的陳述法也是正確，只是沒有像will，把情況表達的那麼清楚而已。l

Amendment: If you do come to the party,please let me know in advance. Yip