Hi, I think I know what you want to do.
First you need to make sure nothing else is setting the scrolling (not sure if you use scrolling to the player or if you have free scrolling in your project).
Easiest way to do it is with some trigonometry, but you also need to store the scroll to points, either create two global variables called scroll2x and scroll2y or add those as instance variables to the player, maybe even create an object that is invisible called camera and have it store all kinds of variables related to scrolling mode. The reason why the latter might be more useful is that you can use the object as a storage for all kinds of boolean variables (like IsScrolling2Portal).
Regardless, here is an example, because it was faster to make this than explains:
https://www.dropbox.com/s/m9f65q4mn5yv0 ... .capx?dl=1
It took me longer than expected to make this, mostly because I forgot the proper order of parameters for distance and angle functions. Mornings are not my best time of the day.
I cheated a bit as I set scroll2x and scroll2y in the same event when picking the random location of the portal tile instead of searching for it in the tile map. Normally you will need to obtain it otherwise somehow, assuming your maps are not randomly generated that should be fairly easy to do.