ok, probably the best thing to do, is to make a 2 x 2 little graphic, make the top-left pixel of an odd color, and also the pixel to the right of it, and the one beneath it. The bottom-right pixel should be a color similar, or hopefully the same of the background (or the color the spot would otherwise be).
Create an actor "spot", or if you plan to make several of these spots in the game, then "spot1'. Put the actor in place BEFORE you add the animation, so you see where it is, otherwise by the time you find it, are able to click on it and move it, you'll get frustrated and all...
In the Collision event of the character, with spot or spot1, do this:
directional_velocity = 0;
//If you don't want to let the player move the character untill the animation is over, then add these lines:
EventDisable();
//Probably it' better to choose the actions through the variables/functions button, and choose to disable the actions which
//would move the actor. As I understand you have a path to move this actor. So here we go:
ChangePath(the paath and actor..);
That's it there. Now to finish it all up, we need a PathFinish for the actor which starts moving:
ChangePath( none...);
//If you want to let your character move when the other came up, then add this too:
EventEnable(events for moving character);
Now if there was no need to stop the player from moving the actor while that comes up, then just take out the Event Enable-disable out. That's about it...
Hope I could help!