The Camera section of commands should have a section dedicated to locking cameras to objects. I don't have WE but check that area. If not, the Player section MIGHT have it.
If that doesn't work, then use a periodic trigger.
Trigger:
Melee Initialization
Events
Conditions
Actions
Unit - Create 1 Dummy for PLAYER at LOC facing Default building facing degrees
Camera - Lock camera target for PLAYER to (Last Created Unit), offset by (0.00, 0.00) using Default rotation
Use a dummy unit so that you can lock it to it. And what I mean by "Periodic Trigger", just add the periodic event for about 0.1 or so and they won't be able to scroll off. (They can, but it will lock back real fast)