How can we differentiate two windows

Hi AutoIT Team,

Can anybody suggest which functions i can use to differentiate between two windows which have the same name, same title and both are opened.

 Actually i was trying to make a script for on MS Outlook , In which

1. I have opened a compose mail and attach a file(say: Q) using attach file button.

2. I again compose a mail and attach another file(SAY:R) using attach outlook item.

So now i have two opened compose mail window with same title, same text but with different attachments.

now 1st i want to send the mail which has the attachment "Q". and then send the mail having attachment "R".

is there any way that i can take the control to window on the basis of the name of the attachment or some other thing you can kindly suggests please..............