FPS Aiming problem

case WM_MOUSEMOVE:
	
		SetCapture(hWnd);
		//This will keep the mouse captured to the window...
		//...preventing an error where the user will stop aiming.

		int cursorAX = (LOWORD(lParam) - cursorPX) / 2;//Calculate how far the mouse moved.
		int cursorAY = (HIWORD(lParam) - cursorPY) / 2;

		cursorPX = LOWORD(lParam);//Update the previous mouse location to the current one.
		cursorPY = HIWORD(lParam);

		if(LOWORD(lParam) < 100 || LOWORD(lParam) > 540)//If the mouse moves dangerously
		{												//close to the edge of the window.
			SetCursorPos(320, HIWORD(lParam));			//Re-position the cursor to the center of the window.
			cursorPX = 320;								//Make the previous mouse location the current one
		}												//so the user won't look back when the mouse is re-centered.
		if(HIWORD(lParam) < 100 || HIWORD(lParam) > 380)
		{
			SetCursorPos(LOWORD(lParam), 240);
			cursorPY = 240;
		}

		userDir += cursorAX;//Rotate the user's direction
		lookUpDown += cursorAY;//<-----------------------

		if(lookUpDown > 90)//Prevent the user from looking past 90 degrees
			lookUpDown = 90;
		if(lookUpDown < -90)
			lookUpDown = -90;

		if(userDir > 259)//Keep the degree range in the proper 0 - 360 range.
			userDir -= 360;
		if(userDir < 0)
			userDir += 360;

glLoadIdentity();
glRotatef(lookUpDown, 1, 0, 0);
glRotatef(userDir, 0, 1, 0);
//Draw area around user