Arraylist combogrouping

Question

Halo to all..  Im new in C#..
Pls. Do help.. I have a problem on creating an array of array.. I have dis settings

comboport = 16 array;
combochannel = 81 array;

In 1 comboport there should be 81 combochannel. First i have to set da comboport into selected index, then select different channel.
And in 1 channel there should be desired combosensor and combooutput used.

first group.

i have dis code.. Selecting da ComboChannel used
private void comboIOChannel_SelectedIndexChanged(object sender, EventArgs e)
{
IOChan = comboIOChannel.SelectedIndex;
comboIOSensor.SelectedIndex = IOSensor[IOChan];
comboOutput.SelectedIndex = IOOutput[IOChan];
}

Main group.... Selecting da comboport used.

private void comboPortIO_SelectedIndexChanged(object sender, EventArgs e)
{
IOPortNumber = comboPort.SelectedIndex;
combochannel.selectedindex = IOChannelNo [IOPortNumber];

comboIOSensor.SelectedIndex = IOSensor[IOPortNumber];

comboOutput.SelectedIndex = IOOutput[IOPortNumber];
}

Now da problem is eveytime i select da comboport, da combosensor and combooutput is not changing on da selected items..
please do help and take a look of my codes.. any ideas Please..
Thanks..