it做形式宾语的用法主要有一下几点：
通常和下列动词连用,代替不定式.
consider, think, make, find, believe, declare, feel, guess, imagine, judge, prove, see, show, suppose, take等.例如：
We consider it our duty to help the old.
I think it important to get along well with others.
上面动词it句型的不定式动词短语前,如：
Many Chinese here find it necessary for them to have a better command of Englsh.
也可以代替动名词与动名词短语成为句子的宾语.例如：
I do not consider it worthwhile spending too much time on telephone conversation.
但你的句子我个人认为（有待于求证）it代替了 if you could offer some help when I am in trouble.因为宾语较长,为了使句子平衡.欢迎指正探讨!共同进步!