If he should come here tomorrow,I would talk to him.

对,
但这些动词的形式是
should + 动词原型
were to + 动词原型
动词过去式
例：
If he should come tomorrow,I would ask for his autograph
If he were to come tomorrow,I would ask for his autograph
If came tomorrow,I would ask for his autograph
这种句子也可以用倒装形式这样说
Should he come tomorrow,I would ask for his autograph
Were he to come tomorrow,I would ask for his autograph
至于何时用哪个,英语很灵活,对这没有语法规定,仅是写作风格的问题而已.
希望帮到了你,
我是加拿大人,英语母语.那为什么还要存在三种形式呢？既然一样一种就够了呀。像虚拟语气现在和过去就只有一种啊。谢谢哈哈哈，如果语言仅有一个表达方式，一个选择，这个世界就不会有散文，诗歌，音乐，歌唱了。。。那生活不是太枯燥了？但我们凡人不必那么紧张，在日常生活里，我们没有必要掌握这些复杂的语法的奥妙之处。对吗？