Is the sentence "I will see the doctor at 2.00 this afternoon so I can't go to the lecture" right? I am confused about the difference between "I will see the doctor at 2.00 this afternoon so I can't go to the lecture" and "I'm seeing the doctor at 2.00 this afternoon so I can't go to the lecture." The grammar book says "i'm seeing" is right but I can't understand why "I will see" is wrong~orz