Instantaneous mass change in Quadcopter;

I am going to use the Aerospace Blockset. Please refer to: http://www.mathworks.it/help/toolbox/aeroblks/customvariablemass6dofeulerangles.html

This block takes into account a body with variable mass, thus a mass flowrate and a dI/dt are reported into the equations.

My task is designing a controller for a sudden change of mass of the UAV (from 0.51Kg to 0.61Kg).

1) Is it possible to add the current mass to the outputs of the Custom Variable Mass 6DOF block?

2) How could you model an instantaneous mass change?

Any help is greatly appreciated. Best regards