I'm trying to create a series of alerts, one of which is when the Aroon Osciallator cross from positive to negative or vice versa.  How can I do that?  Thanks in advance for all help.  :)

If you actually mean an Alert, you can click on the Aroon Oscillator and select Set Alert. You can then choose the requirements of the Alert from the Condition drop-down menu. You would want to choose either Crossing Down Value or Crossing Up Value with the value set to 0.

Setting Alerts in TC2000
Managing Alerts in the Alert Console

Note that Alerts are created for one symbol at a time. If you want to monitor an entire WatchList of symbols at a time, you would need to create a Condition to use as a WatchList Column or EasyScan Condition.

The basic idea of creating a Condition is pretty much the same as setting an Alert. CLick on the Aroon Oscillator and select Create Scan Condition. Then choose the desired condition from the Condition drop-down menu.

Create Conditions from Your Chart
Building a Scan with Multiple Conditions
Sorting with Chart Conditions