gluUnProject with multiple viewports

Im trying to get the opengl mouse coordinates of the 4 viewports that I have

// Set Viewport To Top Left And Draw Window
		glViewport(0, this->S_OpenGLInfo.win32_height / 2, this->S_OpenGLInfo.win32_width / 2, this->S_OpenGLInfo.win32_height / 2);

POINT pos;
		ScreenToClient(this->S_Win32Info[0].hwnd, &pos);
		GLint viewport[4];
		GLdouble modelview[16];
		GLdouble projection[16];
		GLfloat winX, winY, winZ;
		GLdouble posX, posY, posZ;

		glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
		glGetDoublev( GL_PROJECTION_MATRIX, projection );
		glGetIntegerv( GL_VIEWPORT, viewport );

		winX = (float)pos.x;
		winY = (float)viewport[3] - (float)pos.y;
		glReadPixels( pos.x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );

		gluUnProject( winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ);


With this code I dont get the correct coordinates.
And with the 2 lower viewports it gives me 0.0 for both posX and posY.
Thanks in advanced