Articulate Storyline Fit program/browser window size to capture area

Let's assume that for quality purposes you want to record a series of screencasts from time to time at exactly the same program/browser window size, say, 1280x720.

Is there no way, to force a browser/programm, etc. via storyline to adapt to this size and record it? 

My problem is, if I only want do retake a couple of screenshots, I have to retake the whole screencast or otherwise the pixels are "jumping" because the new screenshots aren't fitting exactly to the old ones. 

Looking forward to some ideas!