getSelectOptions problem

I am trying to retrieve all of the select options that start with a certain string when a fieldChanged event is triggered.  But I am getting an error when I call the getSelectOptions() function call.

When the fieldChanged event code is invoked, I set a variable to a different field (a select drop-down) using nlapiGetField('myselect').  This field appears to be valid as I can call getLabel() on it, and it returns the correct value.

So if I do this:

var mySelect = nlapiGetField('myselect');
alert ('label = ' + mySelect.getLabel());

This works.  But if I add the following line, which is the code I really need, it doesn't work.