How do I make two steppers run simultaneously with Matlab R2011a and Arduino ?

Hello

I have an Arduino Uno and the Motor Shield V2 I'm able to control the two steppers with the speed and the rotation angle i want but not at the same time.The code i write at the MATLAB's M-File is this one:

    %  a=arduino('COM3');

 a.stepperSpeed(1,10);
 a.stepperSpeed(2,20);

 a.stepperStep(1,'forward','single',48);
 a.stepperStep(2,'forward','single',48);

The pde file that i upload the Arduino is the motor_V2.pde .

I tried to upload different pde but nothing happend.

Also I tried for Simulinks Support Package i read in another post, but the package is for MATLAB 2012 and I don't want run the motors from simulink.

Is there anyway way for run the motors simultaneously?

Thank you.