sb should be doing in doing

I should be doing right in lending it to him 意思是：我把它借给他应该是对的.
sb should be doing sth 意思是某人应该做某事,指的是一种现在的时态,所以要用be doing的形式.例如：You should be writing carefully.意思是：你（现在）应该写的仔细点.反过来看你说的那句话,i should be doing right（我应该是做对了）,做对了什么事呢?后面解释了这件事 - in lending it to him,这里做对了的事情要用介词in,所以后面应该是in sth/in doing sth.
如果我的回答能够帮助你,