How to implement a biphasic asymmetric waveform?

Hello everyone. I'm trying to figure out how to implement a biphasic asymmetric waveform in Comsol 4.3a. I need to be able to use the following electrical simulator settings in order to stimulate an array of electrodes. Does anyone know how to do such a thing in Comsol? Your help would be greatly appreciated. Thanks.

Here is the information for the 4 channel electrical stimulator settings:

Channels 1+2 output as one biphasic waveform:
Channel 1:
-- Pulse width = 0.160 msec
-- Pulse period = 10 msec
-- Amplitude = 10 V
Channel 2:
-- Pulse width = 5 msec
-- Pulse period = 10 msec
-- Amplitude = -0.32 V

Channels 3+4 output as one biphasic waveform:
Channel 3:
-- Pulse width = 5 msec
-- Pulse period = 10 msec
-- Amplitude = 0.32 V
Channel 4:
-- Pulse width = 0.160 msec
-- Pulse period = 10 msec
-- Amplitude = -10 V

I look forward to hearing from anyone who may be of some help for me on this topic. Thanks again!