Citing with multiple word documents open

Hi everyone, 

Is there a way to make endnote select a specific word document when inserting citations and I have multiple documents open? For work, I usually have one word document open as a reference (which also contains its own endnote bibliography), but that I am note actively typing in, and another one that I am typing in and want to insert my references. But for some reason, endnote tends to select the document that I am using as a reference to insert the citation even though I am not actively typing in it and even if it’s not the last (or first) document I openend. I know I can insert citations directly form the word document, but it takes a lot longer to process and sometimes I need to add multiple citations at once and it becomes very cumbersome.