Hello.This is my first post.I am developing a strategy game like AoE 2 with OpenGL.I need to calculate mouse move amount after left click.My codes so far:

bool mouseMove = false;

POINT firstMouse;

POINT lastMouse;

.
.
.
Render()
{

     float x =firstMouse.x;
     float y =firstMouse.y;


   if(mouse.buttonDown(Mouse::BUTTON_LEFT) && (mouseMove) )
	{

	glColor3f(1.0,0.0,0.0); 

	glLineWidth(2);

	float lastX = lastMouse.x;
	float lastY = lastMouse.y; 
	

	glBegin(GL_LINE_LOOP);
         glVertex2i(x,y);
	     glVertex2i(lastX ,y);
	     glVertex2i(lastX ,lastY);
	     glVertex2i(x,lastY);
	glEnd();

	glFlush();

	glColor3f(1.0,1.0,1.0); 

         }



}

.
.
.

WndProc(HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam)
{

case WM_MOUSEMOVE:
		mouseMove = true;
             GetCursorPos(&lastMouse);
            break;
default:
		mouseMove = false;
           GetCursorPos(&firstMouse);
        break;

}

Thanks.

Thanks a lot It worked with a little change.I am sharing.Maybe, it requires to someone

LRESULT CALLBACK CWindow::WndProc(HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam)
{

	case WM_LBUTTONDOWN:
		GetCursorPos(&lastMouse);
                 break;

	case WM_MOUSEMOVE:
		mouseMove = true;
		break;

	default:
		mouseMove = false;
		GetCursorPos(&firstMouse);
                break;

}