implementing two different quotation styles


in my thesis I would like to use two different styles to cite the literature. One is the “normal” one: A happend because of B (Author, Year). 

The second style should be: a study by Author (Year) showed …

How can I achieve that? I tried to change the style in endnote, but the programme only allows me to implement one style at a time.

I’m sure somebody already asked this question, but I couldn’t find anything via google, nor the search function of this community.

Thank you for your reply!!

Since X5, there is a right click edit citation, that will switch an individual citation from (Author, Year) to Author (Year).