No, it won't work.
The EventArgs class is not an example of a MouseEventArrgs class, rather the other way round: MouseEventArgs derives from EventArgs. So you can cast a MouseEventArgs ro an EventArgs, but you can't go the other way because the computer cannot invent the required information.
Instead, use the Control.MouseButtons property:
MouseButtons mb = MouseButtons;
if (mb == MouseButtons.Right)