Not sure what 'Graphics Mode' means. But you can get input from the mouse by listening to mouse input messages out of the message loop. WM_MOUSEMOVE will return a standard message to you. Loword lparam is x and hiword I believe is y.
WM_LBUTTONDOWN, etc can be used as well.
If the mouse is USB, and most are these days, you can also grab the input out of the RawInput API's. But they are a little trickier. You'll need to know the MOUHID codes..
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I've got spurs that jingle jangle jingle.
As I go riding merrily along.
And they sing, "Oh, ain't you glad you're single?"
And that song ain't so very far from wrong.