Open "**.CSV" For Append As #1 'Append 从文件末尾开始写入，因为文件末所以不存在覆盖
Print #1, A,",",B,",",C,"," ; ‘写入内容为：A B C
Print #1, ’换行 A B C
Print #1, A,",",B,",",C,"," ;
CLOSE #1
Open "**.CSV" For Output As #1 'Output 从文件开头开始写入如果有内容就会覆盖
Print #1, A,",",B,",",C,"," ; ‘写入内容为：A B C
Print #1, ’换行 A B C
Print #1, A,",",B,",",C,"," ;
CLOSE #1
以上内容已经理解的基础上，想实现第一行的 A B C 中的B重写，变成D
ABC → ADC
ABC →ABC 　'第二行不变
除了先读一边，写入数组里，再把内容修改之后重新写入文件
有没有直接指定某一行写入的方法（写入的某行行数已知）
大概就是这样的意思，
CSV文件本身是 A,B,C,这样的字符串，感觉没办法直接实现其中某个字符的修改
有见识广大的同学可以给个思路

位置固定或者你可以得到其位置，则可以用seek，不固定的可以先按规则全部读取数组，替换后覆盖写入