There is a new Mouse event, you can use EVENT_PLAYER_MOUSE_MOVE.
And then fetch it in the event using:
native BlzGetTriggerPlayerMouseX takes nothing returns real
native BlzGetTriggerPlayerMouseY takes nothing returns real
native BlzGetTriggerPlayerMousePosition takes nothing returns location
Ofc you can save this to a variable to fetch it at any time.
Keep in mind that this event is Synced, so there is gonna be a delay.